adding ffmpeg specific version

1 files changed, 1461 insertions, 0 deletions

diff --git a/ffmpeg1/libavformat/matroskaenc.c b/ffmpeg1/libavformat/matroskaenc.c
new file mode 100644
index 0000000..a151eef
--- /dev/null
+++ b/ffmpeg1/libavformat/matroskaenc.c
@@ -0,0 +1,1461 @@
+/*
+ * Matroska muxer
+ * Copyright (c) 2007 David Conrad
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avformat.h"
+#include "internal.h"
+#include "riff.h"
+#include "isom.h"
+#include "matroska.h"
+#include "avc.h"
+#include "flacenc.h"
+#include "avlanguage.h"
+#include "libavutil/samplefmt.h"
+#include "libavutil/sha.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/intfloat.h"
+#include "libavutil/mathematics.h"
+#include "libavutil/random_seed.h"
+#include "libavutil/lfg.h"
+#include "libavutil/dict.h"
+#include "libavutil/avstring.h"
+#include "libavcodec/xiph.h"
+#include "libavcodec/mpeg4audio.h"
+
+typedef struct ebml_master {
+    int64_t         pos;                ///< absolute offset in the file where the master's elements start
+    int             sizebytes;          ///< how many bytes were reserved for the size
+} ebml_master;
+
+typedef struct mkv_seekhead_entry {
+    unsigned int    elementid;
+    uint64_t        segmentpos;
+} mkv_seekhead_entry;
+
+typedef struct mkv_seekhead {
+    int64_t                 filepos;
+    int64_t                 segment_offset;     ///< the file offset to the beginning of the segment
+    int                     reserved_size;      ///< -1 if appending to file
+    int                     max_entries;
+    mkv_seekhead_entry      *entries;
+    int                     num_entries;
+} mkv_seekhead;
+
+typedef struct {
+    uint64_t        pts;
+    int             tracknum;
+    int64_t         cluster_pos;        ///< file offset of the cluster containing the block
+} mkv_cuepoint;
+
+typedef struct {
+    int64_t         segment_offset;
+    mkv_cuepoint    *entries;
+    int             num_entries;
+} mkv_cues;
+
+typedef struct {
+    int             write_dts;
+    int             has_cue;
+} mkv_track;
+
+#define MODE_MATROSKAv2 0x01
+#define MODE_WEBM       0x02
+
+typedef struct MatroskaMuxContext {
+    int             mode;
+    AVIOContext   *dyn_bc;
+    ebml_master     segment;
+    int64_t         segment_offset;
+    ebml_master     cluster;
+    int64_t         cluster_pos;        ///< file offset of the current cluster
+    int64_t         cluster_pts;
+    int64_t         duration_offset;
+    int64_t         duration;
+    mkv_seekhead    *main_seekhead;
+    mkv_cues        *cues;
+    mkv_track       *tracks;
+
+    AVPacket        cur_audio_pkt;
+
+    int have_attachments;
+} MatroskaMuxContext;
+
+
+/** 2 bytes * 3 for EBML IDs, 3 1-byte EBML lengths, 8 bytes for 64 bit
+ * offset, 4 bytes for target EBML ID */
+#define MAX_SEEKENTRY_SIZE 21
+
+/** per-cuepoint-track - 3 1-byte EBML IDs, 3 1-byte EBML sizes, 2
+ * 8-byte uint max */
+#define MAX_CUETRACKPOS_SIZE 22
+
+/** per-cuepoint - 2 1-byte EBML IDs, 2 1-byte EBML sizes, 8-byte uint max */
+#define MAX_CUEPOINT_SIZE(num_tracks) 12 + MAX_CUETRACKPOS_SIZE*num_tracks
+
+
+static int ebml_id_size(unsigned int id)
+{
+    return (av_log2(id+1)-1)/7+1;
+}
+
+static void put_ebml_id(AVIOContext *pb, unsigned int id)
+{
+    int i = ebml_id_size(id);
+    while (i--)
+        avio_w8(pb, (uint8_t)(id >> (i*8)));
+}
+
+/**
+ * Write an EBML size meaning "unknown size".
+ *
+ * @param bytes The number of bytes the size should occupy (maximum: 8).
+ */
+static void put_ebml_size_unknown(AVIOContext *pb, int bytes)
+{
+    av_assert0(bytes <= 8);
+    avio_w8(pb, 0x1ff >> bytes);
+    while (--bytes)
+        avio_w8(pb, 0xff);
+}
+
+/**
+ * Calculate how many bytes are needed to represent a given number in EBML.
+ */
+static int ebml_num_size(uint64_t num)
+{
+    int bytes = 1;
+    while ((num+1) >> bytes*7) bytes++;
+    return bytes;
+}
+
+/**
+ * Write a number in EBML variable length format.
+ *
+ * @param bytes The number of bytes that need to be used to write the number.
+ *              If zero, any number of bytes can be used.
+ */
+static void put_ebml_num(AVIOContext *pb, uint64_t num, int bytes)
+{
+    int i, needed_bytes = ebml_num_size(num);
+
+    // sizes larger than this are currently undefined in EBML
+    av_assert0(num < (1ULL<<56)-1);
+
+    if (bytes == 0)
+        // don't care how many bytes are used, so use the min
+        bytes = needed_bytes;
+    // the bytes needed to write the given size would exceed the bytes
+    // that we need to use, so write unknown size. This shouldn't happen.
+    av_assert0(bytes >= needed_bytes);
+
+    num |= 1ULL << bytes*7;
+    for (i = bytes - 1; i >= 0; i--)
+        avio_w8(pb, (uint8_t)(num >> i*8));
+}
+
+static void put_ebml_uint(AVIOContext *pb, unsigned int elementid, uint64_t val)
+{
+    int i, bytes = 1;
+    uint64_t tmp = val;
+    while (tmp>>=8) bytes++;
+
+    put_ebml_id(pb, elementid);
+    put_ebml_num(pb, bytes, 0);
+    for (i = bytes - 1; i >= 0; i--)
+        avio_w8(pb, (uint8_t)(val >> i*8));
+}
+
+static void put_ebml_float(AVIOContext *pb, unsigned int elementid, double val)
+{
+    put_ebml_id(pb, elementid);
+    put_ebml_num(pb, 8, 0);
+    avio_wb64(pb, av_double2int(val));
+}
+
+static void put_ebml_binary(AVIOContext *pb, unsigned int elementid,
+                            const void *buf, int size)
+{
+    put_ebml_id(pb, elementid);
+    put_ebml_num(pb, size, 0);
+    avio_write(pb, buf, size);
+}
+
+static void put_ebml_string(AVIOContext *pb, unsigned int elementid, const char *str)
+{
+    put_ebml_binary(pb, elementid, str, strlen(str));
+}
+
+/**
+ * Write a void element of a given size. Useful for reserving space in
+ * the file to be written to later.
+ *
+ * @param size The number of bytes to reserve, which must be at least 2.
+ */
+static void put_ebml_void(AVIOContext *pb, uint64_t size)
+{
+    int64_t currentpos = avio_tell(pb);
+
+    av_assert0(size >= 2);
+
+    put_ebml_id(pb, EBML_ID_VOID);
+    // we need to subtract the length needed to store the size from the
+    // size we need to reserve so 2 cases, we use 8 bytes to store the
+    // size if possible, 1 byte otherwise
+    if (size < 10)
+        put_ebml_num(pb, size-1, 0);
+    else
+        put_ebml_num(pb, size-9, 8);
+    while(avio_tell(pb) < currentpos + size)
+        avio_w8(pb, 0);
+}
+
+static ebml_master start_ebml_master(AVIOContext *pb, unsigned int elementid, uint64_t expectedsize)
+{
+    int bytes = expectedsize ? ebml_num_size(expectedsize) : 8;
+    put_ebml_id(pb, elementid);
+    put_ebml_size_unknown(pb, bytes);
+    return (ebml_master){ avio_tell(pb), bytes };
+}
+
+static void end_ebml_master(AVIOContext *pb, ebml_master master)
+{
+    int64_t pos = avio_tell(pb);
+
+    if (avio_seek(pb, master.pos - master.sizebytes, SEEK_SET) < 0)
+        return;
+    put_ebml_num(pb, pos - master.pos, master.sizebytes);
+    avio_seek(pb, pos, SEEK_SET);
+}
+
+static void put_xiph_size(AVIOContext *pb, int size)
+{
+    int i;
+    for (i = 0; i < size / 255; i++)
+        avio_w8(pb, 255);
+    avio_w8(pb, size % 255);
+}
+
+/**
+ * Initialize a mkv_seekhead element to be ready to index level 1 Matroska
+ * elements. If a maximum number of elements is specified, enough space
+ * will be reserved at the current file location to write a seek head of
+ * that size.
+ *
+ * @param segment_offset The absolute offset to the position in the file
+ *                       where the segment begins.
+ * @param numelements The maximum number of elements that will be indexed
+ *                    by this seek head, 0 if unlimited.
+ */
+static mkv_seekhead * mkv_start_seekhead(AVIOContext *pb, int64_t segment_offset, int numelements)
+{
+    mkv_seekhead *new_seekhead = av_mallocz(sizeof(mkv_seekhead));
+    if (new_seekhead == NULL)
+        return NULL;
+
+    new_seekhead->segment_offset = segment_offset;
+
+    if (numelements > 0) {
+        new_seekhead->filepos = avio_tell(pb);
+        // 21 bytes max for a seek entry, 10 bytes max for the SeekHead ID
+        // and size, and 3 bytes to guarantee that an EBML void element
+        // will fit afterwards
+        new_seekhead->reserved_size = numelements * MAX_SEEKENTRY_SIZE + 13;
+        new_seekhead->max_entries = numelements;
+        put_ebml_void(pb, new_seekhead->reserved_size);
+    }
+    return new_seekhead;
+}
+
+static int mkv_add_seekhead_entry(mkv_seekhead *seekhead, unsigned int elementid, uint64_t filepos)
+{
+    mkv_seekhead_entry *entries = seekhead->entries;
+
+    // don't store more elements than we reserved space for
+    if (seekhead->max_entries > 0 && seekhead->max_entries <= seekhead->num_entries)
+        return -1;
+
+    entries = av_realloc(entries, (seekhead->num_entries + 1) * sizeof(mkv_seekhead_entry));
+    if (entries == NULL)
+        return AVERROR(ENOMEM);
+
+    entries[seekhead->num_entries  ].elementid = elementid;
+    entries[seekhead->num_entries++].segmentpos = filepos - seekhead->segment_offset;
+
+    seekhead->entries = entries;
+    return 0;
+}
+
+/**
+ * Write the seek head to the file and free it. If a maximum number of
+ * elements was specified to mkv_start_seekhead(), the seek head will
+ * be written at the location reserved for it. Otherwise, it is written
+ * at the current location in the file.
+ *
+ * @return The file offset where the seekhead was written,
+ * -1 if an error occurred.
+ */
+static int64_t mkv_write_seekhead(AVIOContext *pb, mkv_seekhead *seekhead)
+{
+    ebml_master metaseek, seekentry;
+    int64_t currentpos;
+    int i;
+
+    currentpos = avio_tell(pb);
+
+    if (seekhead->reserved_size > 0) {
+        if (avio_seek(pb, seekhead->filepos, SEEK_SET) < 0) {
+            currentpos = -1;
+            goto fail;
+        }
+    }
+
+    metaseek = start_ebml_master(pb, MATROSKA_ID_SEEKHEAD, seekhead->reserved_size);
+    for (i = 0; i < seekhead->num_entries; i++) {
+        mkv_seekhead_entry *entry = &seekhead->entries[i];
+
+        seekentry = start_ebml_master(pb, MATROSKA_ID_SEEKENTRY, MAX_SEEKENTRY_SIZE);
+
+        put_ebml_id(pb, MATROSKA_ID_SEEKID);
+        put_ebml_num(pb, ebml_id_size(entry->elementid), 0);
+        put_ebml_id(pb, entry->elementid);
+
+        put_ebml_uint(pb, MATROSKA_ID_SEEKPOSITION, entry->segmentpos);
+        end_ebml_master(pb, seekentry);
+    }
+    end_ebml_master(pb, metaseek);
+
+    if (seekhead->reserved_size > 0) {
+        uint64_t remaining = seekhead->filepos + seekhead->reserved_size - avio_tell(pb);
+        put_ebml_void(pb, remaining);
+        avio_seek(pb, currentpos, SEEK_SET);
+
+        currentpos = seekhead->filepos;
+    }
+fail:
+    av_free(seekhead->entries);
+    av_free(seekhead);
+
+    return currentpos;
+}
+
+static mkv_cues * mkv_start_cues(int64_t segment_offset)
+{
+    mkv_cues *cues = av_mallocz(sizeof(mkv_cues));
+    if (cues == NULL)
+        return NULL;
+
+    cues->segment_offset = segment_offset;
+    return cues;
+}
+
+static int mkv_add_cuepoint(mkv_cues *cues, int stream, int64_t ts, int64_t cluster_pos)
+{
+    mkv_cuepoint *entries = cues->entries;
+
+    if (ts < 0)
+        return 0;
+
+    entries = av_realloc(entries, (cues->num_entries + 1) * sizeof(mkv_cuepoint));
+    if (entries == NULL)
+        return AVERROR(ENOMEM);
+
+    entries[cues->num_entries  ].pts = ts;
+    entries[cues->num_entries  ].tracknum = stream + 1;
+    entries[cues->num_entries++].cluster_pos = cluster_pos - cues->segment_offset;
+
+    cues->entries = entries;
+    return 0;
+}
+
+static int64_t mkv_write_cues(AVIOContext *pb, mkv_cues *cues, mkv_track *tracks, int num_tracks)
+{
+    ebml_master cues_element;
+    int64_t currentpos;
+    int i, j;
+
+    currentpos = avio_tell(pb);
+    cues_element = start_ebml_master(pb, MATROSKA_ID_CUES, 0);
+
+    for (i = 0; i < cues->num_entries; i++) {
+        ebml_master cuepoint, track_positions;
+        mkv_cuepoint *entry = &cues->entries[i];
+        uint64_t pts = entry->pts;
+
+        cuepoint = start_ebml_master(pb, MATROSKA_ID_POINTENTRY, MAX_CUEPOINT_SIZE(num_tracks));
+        put_ebml_uint(pb, MATROSKA_ID_CUETIME, pts);
+
+        // put all the entries from different tracks that have the exact same
+        // timestamp into the same CuePoint
+        for (j = 0; j < num_tracks; j++)
+            tracks[j].has_cue = 0;
+        for (j = 0; j < cues->num_entries - i && entry[j].pts == pts; j++) {
+            int tracknum = entry[j].tracknum - 1;
+            av_assert0(tracknum>=0 && tracknum<num_tracks);
+            if (tracks[tracknum].has_cue)
+                continue;
+            tracks[tracknum].has_cue = 1;
+            track_positions = start_ebml_master(pb, MATROSKA_ID_CUETRACKPOSITION, MAX_CUETRACKPOS_SIZE);
+            put_ebml_uint(pb, MATROSKA_ID_CUETRACK          , entry[j].tracknum   );
+            put_ebml_uint(pb, MATROSKA_ID_CUECLUSTERPOSITION, entry[j].cluster_pos);
+            end_ebml_master(pb, track_positions);
+        }
+        i += j - 1;
+        end_ebml_master(pb, cuepoint);
+    }
+    end_ebml_master(pb, cues_element);
+
+    return currentpos;
+}
+
+static int put_xiph_codecpriv(AVFormatContext *s, AVIOContext *pb, AVCodecContext *codec)
+{
+    uint8_t *header_start[3];
+    int header_len[3];
+    int first_header_size;
+    int j;
+
+    if (codec->codec_id == AV_CODEC_ID_VORBIS)
+        first_header_size = 30;
+    else
+        first_header_size = 42;
+
+    if (avpriv_split_xiph_headers(codec->extradata, codec->extradata_size,
+                              first_header_size, header_start, header_len) < 0) {
+        av_log(s, AV_LOG_ERROR, "Extradata corrupt.\n");
+        return -1;
+    }
+
+    avio_w8(pb, 2);                    // number packets - 1
+    for (j = 0; j < 2; j++) {
+        put_xiph_size(pb, header_len[j]);
+    }
+    for (j = 0; j < 3; j++)
+        avio_write(pb, header_start[j], header_len[j]);
+
+    return 0;
+}
+
+static void get_aac_sample_rates(AVFormatContext *s, AVCodecContext *codec, int *sample_rate, int *output_sample_rate)
+{
+    MPEG4AudioConfig mp4ac;
+
+    if (avpriv_mpeg4audio_get_config(&mp4ac, codec->extradata,
+                                     codec->extradata_size * 8, 1) < 0) {
+        av_log(s, AV_LOG_WARNING, "Error parsing AAC extradata, unable to determine samplerate.\n");
+        return;
+    }
+
+    *sample_rate        = mp4ac.sample_rate;
+    *output_sample_rate = mp4ac.ext_sample_rate;
+}
+
+static int mkv_write_codecprivate(AVFormatContext *s, AVIOContext *pb, AVCodecContext *codec, int native_id, int qt_id)
+{
+    AVIOContext *dyn_cp;
+    uint8_t *codecpriv;
+    int ret, codecpriv_size;
+
+    ret = avio_open_dyn_buf(&dyn_cp);
+    if(ret < 0)
+        return ret;
+
+    if (native_id) {
+        if (codec->codec_id == AV_CODEC_ID_VORBIS || codec->codec_id == AV_CODEC_ID_THEORA)
+            ret = put_xiph_codecpriv(s, dyn_cp, codec);
+        else if (codec->codec_id == AV_CODEC_ID_FLAC)
+            ret = ff_flac_write_header(dyn_cp, codec, 1);
+        else if (codec->codec_id == AV_CODEC_ID_H264)
+            ret = ff_isom_write_avcc(dyn_cp, codec->extradata, codec->extradata_size);
+        else if (codec->codec_id == AV_CODEC_ID_ALAC) {
+            if (codec->extradata_size < 36) {
+                av_log(s, AV_LOG_ERROR,
+                       "Invalid extradata found, ALAC expects a 36-byte "
+                       "QuickTime atom.");
+                ret = AVERROR_INVALIDDATA;
+            } else
+                avio_write(dyn_cp, codec->extradata + 12,
+                                   codec->extradata_size - 12);
+        }
+        else if (codec->extradata_size && codec->codec_id != AV_CODEC_ID_TTA)
+            avio_write(dyn_cp, codec->extradata, codec->extradata_size);
+    } else if (codec->codec_type == AVMEDIA_TYPE_VIDEO) {
+        if (qt_id) {
+            if (!codec->codec_tag)
+                codec->codec_tag = ff_codec_get_tag(ff_codec_movvideo_tags, codec->codec_id);
+            if (codec->extradata_size)
+                avio_write(dyn_cp, codec->extradata, codec->extradata_size);
+        } else {
+            if (!codec->codec_tag)
+                codec->codec_tag = ff_codec_get_tag(ff_codec_bmp_tags, codec->codec_id);
+            if (!codec->codec_tag) {
+                av_log(s, AV_LOG_ERROR, "No bmp codec tag found for codec %s\n",
+                       avcodec_get_name(codec->codec_id));
+                ret = AVERROR(EINVAL);
+            }
+
+            ff_put_bmp_header(dyn_cp, codec, ff_codec_bmp_tags, 0);
+        }
+
+    } else if (codec->codec_type == AVMEDIA_TYPE_AUDIO) {
+        unsigned int tag;
+        tag = ff_codec_get_tag(ff_codec_wav_tags, codec->codec_id);
+        if (!tag) {
+            av_log(s, AV_LOG_ERROR, "No wav codec tag found for codec %s\n",
+                   avcodec_get_name(codec->codec_id));
+            ret = AVERROR(EINVAL);
+        }
+        if (!codec->codec_tag)
+            codec->codec_tag = tag;
+
+        ff_put_wav_header(dyn_cp, codec);
+    }
+
+    codecpriv_size = avio_close_dyn_buf(dyn_cp, &codecpriv);
+    if (codecpriv_size)
+        put_ebml_binary(pb, MATROSKA_ID_CODECPRIVATE, codecpriv, codecpriv_size);
+    av_free(codecpriv);
+    return ret;
+}
+
+static int mkv_write_tracks(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    ebml_master tracks;
+    int i, j, ret, default_stream_exists = 0;
+
+    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_TRACKS, avio_tell(pb));
+    if (ret < 0) return ret;
+
+    tracks = start_ebml_master(pb, MATROSKA_ID_TRACKS, 0);
+    for (i = 0; i < s->nb_streams; i++) {
+        AVStream *st = s->streams[i];
+        default_stream_exists |= st->disposition & AV_DISPOSITION_DEFAULT;
+    }
+    for (i = 0; i < s->nb_streams; i++) {
+        AVStream *st = s->streams[i];
+        AVCodecContext *codec = st->codec;
+        ebml_master subinfo, track;
+        int native_id = 0;
+        int qt_id = 0;
+        int bit_depth = av_get_bits_per_sample(codec->codec_id);
+        int sample_rate = codec->sample_rate;
+        int output_sample_rate = 0;
+        AVDictionaryEntry *tag;
+
+        if (codec->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
+            mkv->have_attachments = 1;
+            continue;
+        }
+
+        if (!bit_depth)
+            bit_depth = av_get_bytes_per_sample(codec->sample_fmt) << 3;
+        if (!bit_depth)
+            bit_depth = codec->bits_per_coded_sample;
+
+        if (codec->codec_id == AV_CODEC_ID_AAC)
+            get_aac_sample_rates(s, codec, &sample_rate, &output_sample_rate);
+
+        track = start_ebml_master(pb, MATROSKA_ID_TRACKENTRY, 0);
+        put_ebml_uint (pb, MATROSKA_ID_TRACKNUMBER     , i + 1);
+        put_ebml_uint (pb, MATROSKA_ID_TRACKUID        , i + 1);
+        put_ebml_uint (pb, MATROSKA_ID_TRACKFLAGLACING , 0);    // no lacing (yet)
+
+        if ((tag = av_dict_get(st->metadata, "title", NULL, 0)))
+            put_ebml_string(pb, MATROSKA_ID_TRACKNAME, tag->value);
+        tag = av_dict_get(st->metadata, "language", NULL, 0);
+        put_ebml_string(pb, MATROSKA_ID_TRACKLANGUAGE, tag ? tag->value:"und");
+
+        if (default_stream_exists) {
+            put_ebml_uint(pb, MATROSKA_ID_TRACKFLAGDEFAULT, !!(st->disposition & AV_DISPOSITION_DEFAULT));
+        }
+        if (st->disposition & AV_DISPOSITION_FORCED)
+            put_ebml_uint(pb, MATROSKA_ID_TRACKFLAGFORCED, 1);
+
+        // look for a codec ID string specific to mkv to use,
+        // if none are found, use AVI codes
+        for (j = 0; ff_mkv_codec_tags[j].id != AV_CODEC_ID_NONE; j++) {
+            if (ff_mkv_codec_tags[j].id == codec->codec_id) {
+                put_ebml_string(pb, MATROSKA_ID_CODECID, ff_mkv_codec_tags[j].str);
+                native_id = 1;
+                break;
+            }
+        }
+
+        if (mkv->mode == MODE_WEBM && !(codec->codec_id == AV_CODEC_ID_VP8 ||
+                                        codec->codec_id == AV_CODEC_ID_VORBIS)) {
+            av_log(s, AV_LOG_ERROR,
+                   "Only VP8 video and Vorbis audio are supported for WebM.\n");
+            return AVERROR(EINVAL);
+        }
+
+        switch (codec->codec_type) {
+            case AVMEDIA_TYPE_VIDEO:
+                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_VIDEO);
+                if(st->avg_frame_rate.num && st->avg_frame_rate.den && 1.0/av_q2d(st->avg_frame_rate) > av_q2d(codec->time_base))
+                    put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, 1E9/av_q2d(st->avg_frame_rate));
+                else
+                    put_ebml_uint(pb, MATROSKA_ID_TRACKDEFAULTDURATION, av_q2d(codec->time_base)*1E9);
+
+                if (!native_id &&
+                      ff_codec_get_tag(ff_codec_movvideo_tags, codec->codec_id) &&
+                    (!ff_codec_get_tag(ff_codec_bmp_tags,   codec->codec_id)
+                     || codec->codec_id == AV_CODEC_ID_SVQ1
+                     || codec->codec_id == AV_CODEC_ID_SVQ3
+                     || codec->codec_id == AV_CODEC_ID_CINEPAK))
+                    qt_id = 1;
+
+                if (qt_id)
+                    put_ebml_string(pb, MATROSKA_ID_CODECID, "V_QUICKTIME");
+                else if (!native_id) {
+                    // if there is no mkv-specific codec ID, use VFW mode
+                    put_ebml_string(pb, MATROSKA_ID_CODECID, "V_MS/VFW/FOURCC");
+                    mkv->tracks[i].write_dts = 1;
+                }
+
+                subinfo = start_ebml_master(pb, MATROSKA_ID_TRACKVIDEO, 0);
+                // XXX: interlace flag?
+                put_ebml_uint (pb, MATROSKA_ID_VIDEOPIXELWIDTH , codec->width);
+                put_ebml_uint (pb, MATROSKA_ID_VIDEOPIXELHEIGHT, codec->height);
+
+                if ((tag = av_dict_get(st->metadata, "stereo_mode", NULL, 0)) ||
+                    (tag = av_dict_get( s->metadata, "stereo_mode", NULL, 0))) {
+                    // save stereo mode flag
+                    uint64_t st_mode = MATROSKA_VIDEO_STEREO_MODE_COUNT;
+
+                    for (j=0; j<MATROSKA_VIDEO_STEREO_MODE_COUNT; j++)
+                        if (!strcmp(tag->value, ff_matroska_video_stereo_mode[j])){
+                            st_mode = j;
+                            break;
+                        }
+
+                    if ((mkv->mode == MODE_WEBM && st_mode > 3 && st_mode != 11)
+                        || st_mode >= MATROSKA_VIDEO_STEREO_MODE_COUNT) {
+                        av_log(s, AV_LOG_ERROR,
+                               "The specified stereo mode is not valid.\n");
+                        return AVERROR(EINVAL);
+                    } else
+                        put_ebml_uint(pb, MATROSKA_ID_VIDEOSTEREOMODE, st_mode);
+                }
+
+                if (st->sample_aspect_ratio.num) {
+                    int64_t d_width = av_rescale(codec->width, st->sample_aspect_ratio.num, st->sample_aspect_ratio.den);
+                    if (d_width > INT_MAX) {
+                        av_log(s, AV_LOG_ERROR, "Overflow in display width\n");
+                        return AVERROR(EINVAL);
+                    }
+                    put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYWIDTH , d_width);
+                    put_ebml_uint(pb, MATROSKA_ID_VIDEODISPLAYHEIGHT, codec->height);
+                }
+
+                if (codec->codec_id == AV_CODEC_ID_RAWVIDEO) {
+                    uint32_t color_space = av_le2ne32(codec->codec_tag);
+                    put_ebml_binary(pb, MATROSKA_ID_VIDEOCOLORSPACE, &color_space, sizeof(color_space));
+                }
+                end_ebml_master(pb, subinfo);
+                break;
+
+            case AVMEDIA_TYPE_AUDIO:
+                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_AUDIO);
+
+                if (!native_id)
+                    // no mkv-specific ID, use ACM mode
+                    put_ebml_string(pb, MATROSKA_ID_CODECID, "A_MS/ACM");
+
+                subinfo = start_ebml_master(pb, MATROSKA_ID_TRACKAUDIO, 0);
+                put_ebml_uint  (pb, MATROSKA_ID_AUDIOCHANNELS    , codec->channels);
+                put_ebml_float (pb, MATROSKA_ID_AUDIOSAMPLINGFREQ, sample_rate);
+                if (output_sample_rate)
+                    put_ebml_float(pb, MATROSKA_ID_AUDIOOUTSAMPLINGFREQ, output_sample_rate);
+                if (bit_depth)
+                    put_ebml_uint(pb, MATROSKA_ID_AUDIOBITDEPTH, bit_depth);
+                end_ebml_master(pb, subinfo);
+                break;
+
+            case AVMEDIA_TYPE_SUBTITLE:
+                put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, MATROSKA_TRACK_TYPE_SUBTITLE);
+                if (!native_id) {
+                    av_log(s, AV_LOG_ERROR, "Subtitle codec %d is not supported.\n", codec->codec_id);
+                    return AVERROR(ENOSYS);
+                }
+                break;
+            default:
+                av_log(s, AV_LOG_ERROR, "Only audio, video, and subtitles are supported for Matroska.\n");
+                break;
+        }
+        ret = mkv_write_codecprivate(s, pb, codec, native_id, qt_id);
+        if (ret < 0) return ret;
+
+        end_ebml_master(pb, track);
+
+        // ms precision is the de-facto standard timescale for mkv files
+        avpriv_set_pts_info(st, 64, 1, 1000);
+    }
+    end_ebml_master(pb, tracks);
+    return 0;
+}
+
+static int mkv_write_chapters(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    ebml_master chapters, editionentry;
+    AVRational scale = {1, 1E9};
+    int i, ret;
+
+    if (!s->nb_chapters)
+        return 0;
+
+    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_CHAPTERS, avio_tell(pb));
+    if (ret < 0) return ret;
+
+    chapters     = start_ebml_master(pb, MATROSKA_ID_CHAPTERS    , 0);
+    editionentry = start_ebml_master(pb, MATROSKA_ID_EDITIONENTRY, 0);
+    put_ebml_uint(pb, MATROSKA_ID_EDITIONFLAGDEFAULT, 1);
+    put_ebml_uint(pb, MATROSKA_ID_EDITIONFLAGHIDDEN , 0);
+    for (i = 0; i < s->nb_chapters; i++) {
+        ebml_master chapteratom, chapterdisplay;
+        AVChapter *c     = s->chapters[i];
+        AVDictionaryEntry *t = NULL;
+
+        chapteratom = start_ebml_master(pb, MATROSKA_ID_CHAPTERATOM, 0);
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERUID, c->id);
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMESTART,
+                      av_rescale_q(c->start, c->time_base, scale));
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERTIMEEND,
+                      av_rescale_q(c->end,   c->time_base, scale));
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERFLAGHIDDEN , 0);
+        put_ebml_uint(pb, MATROSKA_ID_CHAPTERFLAGENABLED, 1);
+        if ((t = av_dict_get(c->metadata, "title", NULL, 0))) {
+            chapterdisplay = start_ebml_master(pb, MATROSKA_ID_CHAPTERDISPLAY, 0);
+            put_ebml_string(pb, MATROSKA_ID_CHAPSTRING, t->value);
+            put_ebml_string(pb, MATROSKA_ID_CHAPLANG  , "und");
+            end_ebml_master(pb, chapterdisplay);
+        }
+        end_ebml_master(pb, chapteratom);
+    }
+    end_ebml_master(pb, editionentry);
+    end_ebml_master(pb, chapters);
+    return 0;
+}
+
+static void mkv_write_simpletag(AVIOContext *pb, AVDictionaryEntry *t)
+{
+    uint8_t *key = av_strdup(t->key);
+    uint8_t *p   = key;
+    const uint8_t *lang = NULL;
+    ebml_master tag;
+
+    if ((p = strrchr(p, '-')) &&
+        (lang = av_convert_lang_to(p + 1, AV_LANG_ISO639_2_BIBL)))
+        *p = 0;
+
+    p = key;
+    while (*p) {
+        if (*p == ' ')
+            *p = '_';
+        else if (*p >= 'a' && *p <= 'z')
+            *p -= 'a' - 'A';
+        p++;
+    }
+
+    tag = start_ebml_master(pb, MATROSKA_ID_SIMPLETAG, 0);
+    put_ebml_string(pb, MATROSKA_ID_TAGNAME, key);
+    if (lang)
+        put_ebml_string(pb, MATROSKA_ID_TAGLANG, lang);
+    put_ebml_string(pb, MATROSKA_ID_TAGSTRING, t->value);
+    end_ebml_master(pb, tag);
+
+    av_freep(&key);
+}
+
+static int mkv_write_tag(AVFormatContext *s, AVDictionary *m, unsigned int elementid,
+                         unsigned int uid, ebml_master *tags)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    ebml_master tag, targets;
+    AVDictionaryEntry *t = NULL;
+    int ret;
+
+    if (!tags->pos) {
+        ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_TAGS, avio_tell(s->pb));
+        if (ret < 0) return ret;
+
+        *tags = start_ebml_master(s->pb, MATROSKA_ID_TAGS, 0);
+    }
+
+    tag     = start_ebml_master(s->pb, MATROSKA_ID_TAG,        0);
+    targets = start_ebml_master(s->pb, MATROSKA_ID_TAGTARGETS, 0);
+    if (elementid)
+        put_ebml_uint(s->pb, elementid, uid);
+    end_ebml_master(s->pb, targets);
+
+    while ((t = av_dict_get(m, "", t, AV_DICT_IGNORE_SUFFIX)))
+        if (av_strcasecmp(t->key, "title") && av_strcasecmp(t->key, "stereo_mode"))
+            mkv_write_simpletag(s->pb, t);
+
+    end_ebml_master(s->pb, tag);
+    return 0;
+}
+
+static int mkv_write_tags(AVFormatContext *s)
+{
+    ebml_master tags = {0};
+    int i, ret;
+
+    ff_metadata_conv_ctx(s, ff_mkv_metadata_conv, NULL);
+
+    if (av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
+        ret = mkv_write_tag(s, s->metadata, 0, 0, &tags);
+        if (ret < 0) return ret;
+    }
+
+    for (i = 0; i < s->nb_streams; i++) {
+        AVStream *st = s->streams[i];
+
+        if (!av_dict_get(st->metadata, "", 0, AV_DICT_IGNORE_SUFFIX))
+            continue;
+
+        ret = mkv_write_tag(s, st->metadata, MATROSKA_ID_TAGTARGETS_TRACKUID, i + 1, &tags);
+        if (ret < 0) return ret;
+    }
+
+    for (i = 0; i < s->nb_chapters; i++) {
+        AVChapter *ch = s->chapters[i];
+
+        if (!av_dict_get(ch->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
+            continue;
+
+        ret = mkv_write_tag(s, ch->metadata, MATROSKA_ID_TAGTARGETS_CHAPTERUID, ch->id, &tags);
+        if (ret < 0) return ret;
+    }
+
+    if (tags.pos)
+        end_ebml_master(s->pb, tags);
+    return 0;
+}
+
+static int mkv_write_attachments(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    ebml_master attachments;
+    AVLFG c;
+    int i, ret;
+
+    if (!mkv->have_attachments)
+        return 0;
+
+    av_lfg_init(&c, av_get_random_seed());
+
+    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_ATTACHMENTS, avio_tell(pb));
+    if (ret < 0) return ret;
+
+    attachments = start_ebml_master(pb, MATROSKA_ID_ATTACHMENTS, 0);
+
+    for (i = 0; i < s->nb_streams; i++) {
+        AVStream *st = s->streams[i];
+        ebml_master attached_file;
+        AVDictionaryEntry *t;
+        const char *mimetype = NULL;
+        uint64_t fileuid;
+
+        if (st->codec->codec_type != AVMEDIA_TYPE_ATTACHMENT)
+            continue;
+
+        attached_file = start_ebml_master(pb, MATROSKA_ID_ATTACHEDFILE, 0);
+
+        if (t = av_dict_get(st->metadata, "title", NULL, 0))
+            put_ebml_string(pb, MATROSKA_ID_FILEDESC, t->value);
+        if (!(t = av_dict_get(st->metadata, "filename", NULL, 0))) {
+            av_log(s, AV_LOG_ERROR, "Attachment stream %d has no filename tag.\n", i);
+            return AVERROR(EINVAL);
+        }
+        put_ebml_string(pb, MATROSKA_ID_FILENAME, t->value);
+        if (t = av_dict_get(st->metadata, "mimetype", NULL, 0))
+            mimetype = t->value;
+        else if (st->codec->codec_id != AV_CODEC_ID_NONE ) {
+            int i;
+            for (i = 0; ff_mkv_mime_tags[i].id != AV_CODEC_ID_NONE; i++)
+                if (ff_mkv_mime_tags[i].id == st->codec->codec_id) {
+                    mimetype = ff_mkv_mime_tags[i].str;
+                    break;
+                }
+        }
+        if (!mimetype) {
+            av_log(s, AV_LOG_ERROR, "Attachment stream %d has no mimetype tag and "
+                                    "it cannot be deduced from the codec id.\n", i);
+            return AVERROR(EINVAL);
+        }
+
+        if (st->codec->flags & CODEC_FLAG_BITEXACT) {
+            struct AVSHA *sha = av_sha_alloc();
+            uint8_t digest[20];
+            if (!sha)
+                return AVERROR(ENOMEM);
+            av_sha_init(sha, 160);
+            av_sha_update(sha, st->codec->extradata, st->codec->extradata_size);
+            av_sha_final(sha, digest);
+            av_free(sha);
+            fileuid = AV_RL64(digest);
+        } else {
+            fileuid = av_lfg_get(&c);
+        }
+        av_log(s, AV_LOG_VERBOSE, "Using %.16"PRIx64" for attachment %d\n",
+               fileuid, i);
+
+        put_ebml_string(pb, MATROSKA_ID_FILEMIMETYPE, mimetype);
+        put_ebml_binary(pb, MATROSKA_ID_FILEDATA, st->codec->extradata, st->codec->extradata_size);
+        put_ebml_uint(pb, MATROSKA_ID_FILEUID, fileuid);
+        end_ebml_master(pb, attached_file);
+    }
+    end_ebml_master(pb, attachments);
+
+    return 0;
+}
+
+static int mkv_write_header(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    ebml_master ebml_header, segment_info;
+    AVDictionaryEntry *tag;
+    int ret, i;
+
+    if (!strcmp(s->oformat->name, "webm")) mkv->mode = MODE_WEBM;
+    else                                   mkv->mode = MODE_MATROSKAv2;
+
+    if (s->avoid_negative_ts < 0)
+        s->avoid_negative_ts = 1;
+
+    for (i = 0; i < s->nb_streams; i++)
+        if (s->streams[i]->codec->codec_id == AV_CODEC_ID_ATRAC3 ||
+            s->streams[i]->codec->codec_id == AV_CODEC_ID_COOK ||
+            s->streams[i]->codec->codec_id == AV_CODEC_ID_RA_288 ||
+            s->streams[i]->codec->codec_id == AV_CODEC_ID_SIPR ||
+            s->streams[i]->codec->codec_id == AV_CODEC_ID_RV10 ||
+            s->streams[i]->codec->codec_id == AV_CODEC_ID_RV20) {
+            av_log(s, AV_LOG_ERROR,
+                   "The Matroska muxer does not yet support muxing %s\n",
+                   avcodec_get_name(s->streams[i]->codec->codec_id));
+            return AVERROR_PATCHWELCOME;
+        }
+
+    mkv->tracks = av_mallocz(s->nb_streams * sizeof(*mkv->tracks));
+    if (!mkv->tracks)
+        return AVERROR(ENOMEM);
+
+    ebml_header = start_ebml_master(pb, EBML_ID_HEADER, 0);
+    put_ebml_uint   (pb, EBML_ID_EBMLVERSION        ,           1);
+    put_ebml_uint   (pb, EBML_ID_EBMLREADVERSION    ,           1);
+    put_ebml_uint   (pb, EBML_ID_EBMLMAXIDLENGTH    ,           4);
+    put_ebml_uint   (pb, EBML_ID_EBMLMAXSIZELENGTH  ,           8);
+    put_ebml_string (pb, EBML_ID_DOCTYPE            , s->oformat->name);
+    put_ebml_uint   (pb, EBML_ID_DOCTYPEVERSION     ,           2);
+    put_ebml_uint   (pb, EBML_ID_DOCTYPEREADVERSION ,           2);
+    end_ebml_master(pb, ebml_header);
+
+    mkv->segment = start_ebml_master(pb, MATROSKA_ID_SEGMENT, 0);
+    mkv->segment_offset = avio_tell(pb);
+
+    // we write 2 seek heads - one at the end of the file to point to each
+    // cluster, and one at the beginning to point to all other level one
+    // elements (including the seek head at the end of the file), which
+    // isn't more than 10 elements if we only write one of each other
+    // currently defined level 1 element
+    mkv->main_seekhead    = mkv_start_seekhead(pb, mkv->segment_offset, 10);
+    if (!mkv->main_seekhead)
+        return AVERROR(ENOMEM);
+
+    ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_INFO, avio_tell(pb));
+    if (ret < 0) return ret;
+
+    segment_info = start_ebml_master(pb, MATROSKA_ID_INFO, 0);
+    put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, 1000000);
+    if ((tag = av_dict_get(s->metadata, "title", NULL, 0)))
+        put_ebml_string(pb, MATROSKA_ID_TITLE, tag->value);
+    if (!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)) {
+        uint32_t segment_uid[4];
+        AVLFG lfg;
+
+        av_lfg_init(&lfg, av_get_random_seed());
+
+        for (i = 0; i < 4; i++)
+            segment_uid[i] = av_lfg_get(&lfg);
+
+        put_ebml_string(pb, MATROSKA_ID_MUXINGAPP , LIBAVFORMAT_IDENT);
+        put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);
+        put_ebml_binary(pb, MATROSKA_ID_SEGMENTUID, segment_uid, 16);
+    }
+
+    if (tag = av_dict_get(s->metadata, "creation_time", NULL, 0)) {
+        // Adjust time so it's relative to 2001-01-01 and convert to nanoseconds.
+        int64_t date_utc = (ff_iso8601_to_unix_time(tag->value) - 978307200) * 1000000000;
+        uint8_t date_utc_buf[8];
+        AV_WB64(date_utc_buf, date_utc);
+        put_ebml_binary(pb, MATROSKA_ID_DATEUTC, date_utc_buf, 8);
+    }
+
+    // reserve space for the duration
+    mkv->duration = 0;
+    mkv->duration_offset = avio_tell(pb);
+    put_ebml_void(pb, 11);                  // assumes double-precision float to be written
+    end_ebml_master(pb, segment_info);
+
+    ret = mkv_write_tracks(s);
+    if (ret < 0) return ret;
+
+    if (mkv->mode != MODE_WEBM) {
+        ret = mkv_write_chapters(s);
+        if (ret < 0) return ret;
+
+        ret = mkv_write_tags(s);
+        if (ret < 0) return ret;
+
+        ret = mkv_write_attachments(s);
+        if (ret < 0) return ret;
+    }
+
+    if (!s->pb->seekable)
+        mkv_write_seekhead(pb, mkv->main_seekhead);
+
+    mkv->cues = mkv_start_cues(mkv->segment_offset);
+    if (mkv->cues == NULL)
+        return AVERROR(ENOMEM);
+
+    av_init_packet(&mkv->cur_audio_pkt);
+    mkv->cur_audio_pkt.size = 0;
+    mkv->cluster_pos = -1;
+
+    avio_flush(pb);
+    return 0;
+}
+
+static int mkv_blockgroup_size(int pkt_size)
+{
+    int size = pkt_size + 4;
+    size += ebml_num_size(size);
+    size += 2;              // EBML ID for block and block duration
+    size += 8;              // max size of block duration
+    size += ebml_num_size(size);
+    size += 1;              // blockgroup EBML ID
+    return size;
+}
+
+static int ass_get_duration(const uint8_t *p)
+{
+    int sh, sm, ss, sc, eh, em, es, ec;
+    uint64_t start, end;
+
+    if (sscanf(p, "%*[^,],%d:%d:%d%*c%d,%d:%d:%d%*c%d",
+               &sh, &sm, &ss, &sc, &eh, &em, &es, &ec) != 8)
+        return 0;
+    start = 3600000LL*sh + 60000LL*sm + 1000LL*ss + 10LL*sc;
+    end   = 3600000LL*eh + 60000LL*em + 1000LL*es + 10LL*ec;
+    return end - start;
+}
+
+static int mkv_write_ass_blocks(AVFormatContext *s, AVIOContext *pb, AVPacket *pkt)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    int i, layer = 0, max_duration = 0, size, line_size, data_size = pkt->size;
+    uint8_t *start, *end, *data = pkt->data;
+    ebml_master blockgroup;
+    char buffer[2048];
+
+    while (data_size) {
+        int duration = ass_get_duration(data);
+        max_duration = FFMAX(duration, max_duration);
+        end = memchr(data, '\n', data_size);
+        size = line_size = end ? end-data+1 : data_size;
+        size -= end ? (end[-1]=='\r')+1 : 0;
+        start = data;
+        for (i=0; i<3; i++, start++)
+            if (!(start = memchr(start, ',', size-(start-data))))
+                return max_duration;
+        size -= start - data;
+        sscanf(data, "Dialogue: %d,", &layer);
+        i = snprintf(buffer, sizeof(buffer), "%"PRId64",%d,",
+                     s->streams[pkt->stream_index]->nb_frames, layer);
+        size = FFMIN(i+size, sizeof(buffer));
+        memcpy(buffer+i, start, size-i);
+
+        av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
+               "pts %" PRId64 ", duration %d\n",
+               avio_tell(pb), size, pkt->pts, duration);
+        blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, mkv_blockgroup_size(size));
+        put_ebml_id(pb, MATROSKA_ID_BLOCK);
+        put_ebml_num(pb, size+4, 0);
+        avio_w8(pb, 0x80 | (pkt->stream_index + 1));     // this assumes stream_index is less than 126
+        avio_wb16(pb, pkt->pts - mkv->cluster_pts);
+        avio_w8(pb, 0);
+        avio_write(pb, buffer, size);
+        put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
+        end_ebml_master(pb, blockgroup);
+
+        data += line_size;
+        data_size -= line_size;
+    }
+
+    return max_duration;
+}
+
+static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
+                            unsigned int blockid, AVPacket *pkt, int flags)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
+    uint8_t *data = NULL;
+    int offset = 0, size = pkt->size;
+    int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
+
+    av_log(s, AV_LOG_DEBUG, "Writing block at offset %" PRIu64 ", size %d, "
+           "pts %" PRId64 ", dts %" PRId64 ", duration %d, flags %d\n",
+           avio_tell(pb), pkt->size, pkt->pts, pkt->dts, pkt->duration, flags);
+    if (codec->codec_id == AV_CODEC_ID_H264 && codec->extradata_size > 0 &&
+        (AV_RB24(codec->extradata) == 1 || AV_RB32(codec->extradata) == 1))
+        ff_avc_parse_nal_units_buf(pkt->data, &data, &size);
+    else
+        data = pkt->data;
+
+    if (codec->codec_id == AV_CODEC_ID_PRORES) {
+        /* Matroska specification requires to remove the first QuickTime atom
+         */
+        size -= 8;
+        offset = 8;
+    }
+
+    put_ebml_id(pb, blockid);
+    put_ebml_num(pb, size+4, 0);
+    avio_w8(pb, 0x80 | (pkt->stream_index + 1));     // this assumes stream_index is less than 126
+    avio_wb16(pb, ts - mkv->cluster_pts);
+    avio_w8(pb, flags);
+    avio_write(pb, data + offset, size);
+    if (data != pkt->data)
+        av_free(data);
+}
+
+static int srt_get_duration(uint8_t **buf)
+{
+    int i, duration = 0;
+
+    for (i=0; i<2 && !duration; i++) {
+        int s_hour, s_min, s_sec, s_hsec, e_hour, e_min, e_sec, e_hsec;
+        if (sscanf(*buf, "%d:%2d:%2d%*1[,.]%3d --> %d:%2d:%2d%*1[,.]%3d",
+                   &s_hour, &s_min, &s_sec, &s_hsec,
+                   &e_hour, &e_min, &e_sec, &e_hsec) == 8) {
+            s_min  +=   60*s_hour;      e_min  +=   60*e_hour;
+            s_sec  +=   60*s_min;       e_sec  +=   60*e_min;
+            s_hsec += 1000*s_sec;       e_hsec += 1000*e_sec;
+            duration = e_hsec - s_hsec;
+        }
+        *buf += strcspn(*buf, "\n") + 1;
+    }
+    return duration;
+}
+
+static int mkv_write_srt_blocks(AVFormatContext *s, AVIOContext *pb, AVPacket *pkt)
+{
+    ebml_master blockgroup;
+    AVPacket pkt2 = *pkt;
+    int64_t duration = srt_get_duration(&pkt2.data);
+    pkt2.size -= pkt2.data - pkt->data;
+
+    blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP,
+                                   mkv_blockgroup_size(pkt2.size));
+    mkv_write_block(s, pb, MATROSKA_ID_BLOCK, &pkt2, 0);
+    put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
+    end_ebml_master(pb, blockgroup);
+
+    return duration;
+}
+
+static void mkv_flush_dynbuf(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    int bufsize;
+    uint8_t *dyn_buf;
+
+    if (!mkv->dyn_bc)
+        return;
+
+    bufsize = avio_close_dyn_buf(mkv->dyn_bc, &dyn_buf);
+    avio_write(s->pb, dyn_buf, bufsize);
+    av_free(dyn_buf);
+    mkv->dyn_bc = NULL;
+}
+
+static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
+    int keyframe = !!(pkt->flags & AV_PKT_FLAG_KEY);
+    int duration = pkt->duration;
+    int ret;
+    int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
+
+    if (ts == AV_NOPTS_VALUE) {
+        av_log(s, AV_LOG_ERROR, "Can't write packet with unknown timestamp\n");
+        return AVERROR(EINVAL);
+    }
+
+    if (!s->pb->seekable) {
+        if (!mkv->dyn_bc) {
+            if ((ret = avio_open_dyn_buf(&mkv->dyn_bc)) < 0) {
+                av_log(s, AV_LOG_ERROR, "Failed to open dynamic buffer\n");
+                return ret;
+            }
+        }
+        pb = mkv->dyn_bc;
+    }
+
+    if (mkv->cluster_pos == -1) {
+        mkv->cluster_pos = avio_tell(s->pb);
+        mkv->cluster = start_ebml_master(pb, MATROSKA_ID_CLUSTER, 0);
+        put_ebml_uint(pb, MATROSKA_ID_CLUSTERTIMECODE, FFMAX(0, ts));
+        mkv->cluster_pts = FFMAX(0, ts);
+    }
+
+    if (codec->codec_type != AVMEDIA_TYPE_SUBTITLE) {
+        mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe << 7);
+    } else if (codec->codec_id == AV_CODEC_ID_SSA) {
+        duration = mkv_write_ass_blocks(s, pb, pkt);
+    } else if (codec->codec_id == AV_CODEC_ID_SRT) {
+        duration = mkv_write_srt_blocks(s, pb, pkt);
+    } else {
+        ebml_master blockgroup = start_ebml_master(pb, MATROSKA_ID_BLOCKGROUP, mkv_blockgroup_size(pkt->size));
+        /* For backward compatibility, prefer convergence_duration. */
+        if (pkt->convergence_duration > 0) {
+            duration = pkt->convergence_duration;
+        }
+        mkv_write_block(s, pb, MATROSKA_ID_BLOCK, pkt, 0);
+        put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, duration);
+        end_ebml_master(pb, blockgroup);
+    }
+
+    if (codec->codec_type == AVMEDIA_TYPE_VIDEO && keyframe) {
+        ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, ts, mkv->cluster_pos);
+        if (ret < 0) return ret;
+    }
+
+    mkv->duration = FFMAX(mkv->duration, ts + duration);
+    return 0;
+}
+
+static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb->seekable ? s->pb : mkv->dyn_bc;
+    AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
+    int ret, keyframe = !!(pkt->flags & AV_PKT_FLAG_KEY);
+    int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
+    int cluster_size = avio_tell(pb) - (s->pb->seekable ? mkv->cluster_pos : 0);
+
+    // start a new cluster every 5 MB or 5 sec, or 32k / 1 sec for streaming or
+    // after 4k and on a keyframe
+    if (mkv->cluster_pos != -1 &&
+        ((!s->pb->seekable && (cluster_size > 32*1024 || ts > mkv->cluster_pts + 1000))
+         ||                      cluster_size > 5*1024*1024 || ts > mkv->cluster_pts + 5000
+         || (codec->codec_type == AVMEDIA_TYPE_VIDEO && keyframe && cluster_size > 4*1024))) {
+        av_log(s, AV_LOG_DEBUG, "Starting new cluster at offset %" PRIu64
+               " bytes, pts %" PRIu64 "\n", avio_tell(pb), ts);
+        end_ebml_master(pb, mkv->cluster);
+        mkv->cluster_pos = -1;
+        if (mkv->dyn_bc)
+            mkv_flush_dynbuf(s);
+    }
+
+    // check if we have an audio packet cached
+    if (mkv->cur_audio_pkt.size > 0) {
+        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
+        av_free_packet(&mkv->cur_audio_pkt);
+        if (ret < 0) {
+            av_log(s, AV_LOG_ERROR, "Could not write cached audio packet ret:%d\n", ret);
+            return ret;
+        }
+    }
+
+    // buffer an audio packet to ensure the packet containing the video
+    // keyframe's timecode is contained in the same cluster for WebM
+    if (codec->codec_type == AVMEDIA_TYPE_AUDIO) {
+        mkv->cur_audio_pkt = *pkt;
+        mkv->cur_audio_pkt.buf = av_buffer_ref(pkt->buf);
+        ret = mkv->cur_audio_pkt.buf ? 0 : AVERROR(ENOMEM);
+    } else
+        ret = mkv_write_packet_internal(s, pkt);
+    return ret;
+}
+
+static int mkv_write_trailer(AVFormatContext *s)
+{
+    MatroskaMuxContext *mkv = s->priv_data;
+    AVIOContext *pb = s->pb;
+    int64_t currentpos, cuespos;
+    int ret;
+
+    // check if we have an audio packet cached
+    if (mkv->cur_audio_pkt.size > 0) {
+        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
+        av_free_packet(&mkv->cur_audio_pkt);
+        if (ret < 0) {
+            av_log(s, AV_LOG_ERROR, "Could not write cached audio packet ret:%d\n", ret);
+            return ret;
+        }
+    }
+
+    if (mkv->dyn_bc) {
+        end_ebml_master(mkv->dyn_bc, mkv->cluster);
+        mkv_flush_dynbuf(s);
+    } else if (mkv->cluster_pos != -1) {
+        end_ebml_master(pb, mkv->cluster);
+    }
+
+    if (pb->seekable) {
+        if (mkv->cues->num_entries) {
+            cuespos = mkv_write_cues(pb, mkv->cues, mkv->tracks, s->nb_streams);
+
+            ret = mkv_add_seekhead_entry(mkv->main_seekhead, MATROSKA_ID_CUES, cuespos);
+            if (ret < 0) return ret;
+        }
+
+        mkv_write_seekhead(pb, mkv->main_seekhead);
+
+        // update the duration
+        av_log(s, AV_LOG_DEBUG, "end duration = %" PRIu64 "\n", mkv->duration);
+        currentpos = avio_tell(pb);
+        avio_seek(pb, mkv->duration_offset, SEEK_SET);
+        put_ebml_float(pb, MATROSKA_ID_DURATION, mkv->duration);
+
+        avio_seek(pb, currentpos, SEEK_SET);
+    }
+
+    end_ebml_master(pb, mkv->segment);
+    av_free(mkv->tracks);
+    av_freep(&mkv->cues->entries);
+    av_freep(&mkv->cues);
+
+    return 0;
+}
+
+static int mkv_query_codec(enum AVCodecID codec_id, int std_compliance)
+{
+    int i;
+    for (i = 0; ff_mkv_codec_tags[i].id != AV_CODEC_ID_NONE; i++)
+        if (ff_mkv_codec_tags[i].id == codec_id)
+            return 1;
+
+    if (std_compliance < FF_COMPLIANCE_NORMAL) {                // mkv theoretically supports any
+        enum AVMediaType type = avcodec_get_type(codec_id);     // video/audio through VFW/ACM
+        if (type == AVMEDIA_TYPE_VIDEO || type == AVMEDIA_TYPE_AUDIO)
+            return 1;
+    }
+
+    return 0;
+}
+
+const AVCodecTag additional_audio_tags[] = {
+    { AV_CODEC_ID_ALAC,      0XFFFFFFFF },
+    { AV_CODEC_ID_EAC3,      0XFFFFFFFF },
+    { AV_CODEC_ID_MLP,       0xFFFFFFFF },
+    { AV_CODEC_ID_OPUS,      0xFFFFFFFF },
+    { AV_CODEC_ID_PCM_S16BE, 0xFFFFFFFF },
+    { AV_CODEC_ID_PCM_S24BE, 0xFFFFFFFF },
+    { AV_CODEC_ID_PCM_S32BE, 0xFFFFFFFF },
+    { AV_CODEC_ID_QDM2,      0xFFFFFFFF },
+    { AV_CODEC_ID_RA_144,    0xFFFFFFFF },
+    { AV_CODEC_ID_RA_288,    0xFFFFFFFF },
+    { AV_CODEC_ID_COOK,      0xFFFFFFFF },
+    { AV_CODEC_ID_TRUEHD,    0xFFFFFFFF },
+    { AV_CODEC_ID_WAVPACK,   0xFFFFFFFF },
+    { AV_CODEC_ID_NONE,      0xFFFFFFFF }
+};
+
+const AVCodecTag additional_video_tags[] = {
+    { AV_CODEC_ID_PRORES,    0xFFFFFFFF },
+    { AV_CODEC_ID_RV10,      0xFFFFFFFF },
+    { AV_CODEC_ID_RV20,      0xFFFFFFFF },
+    { AV_CODEC_ID_RV30,      0xFFFFFFFF },
+    { AV_CODEC_ID_RV40,      0xFFFFFFFF },
+    { AV_CODEC_ID_VP9,       0xFFFFFFFF },
+    { AV_CODEC_ID_NONE,      0xFFFFFFFF }
+};
+
+#if CONFIG_MATROSKA_MUXER
+AVOutputFormat ff_matroska_muxer = {
+    .name              = "matroska",
+    .long_name         = NULL_IF_CONFIG_SMALL("Matroska"),
+    .mime_type         = "video/x-matroska",
+    .extensions        = "mkv",
+    .priv_data_size    = sizeof(MatroskaMuxContext),
+    .audio_codec       = CONFIG_LIBVORBIS_ENCODER ?
+                         AV_CODEC_ID_VORBIS : AV_CODEC_ID_AC3,
+    .video_codec       = CONFIG_LIBX264_ENCODER ?
+                         AV_CODEC_ID_H264 : AV_CODEC_ID_MPEG4,
+    .write_header      = mkv_write_header,
+    .write_packet      = mkv_write_packet,
+    .write_trailer     = mkv_write_trailer,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
+                         AVFMT_TS_NONSTRICT,
+    .codec_tag         = (const AVCodecTag* const []){
+         ff_codec_bmp_tags, ff_codec_wav_tags,
+         additional_audio_tags, additional_video_tags, 0
+    },
+    .subtitle_codec    = AV_CODEC_ID_SSA,
+    .query_codec       = mkv_query_codec,
+};
+#endif
+
+#if CONFIG_WEBM_MUXER
+AVOutputFormat ff_webm_muxer = {
+    .name              = "webm",
+    .long_name         = NULL_IF_CONFIG_SMALL("WebM"),
+    .mime_type         = "video/webm",
+    .extensions        = "webm",
+    .priv_data_size    = sizeof(MatroskaMuxContext),
+    .audio_codec       = AV_CODEC_ID_VORBIS,
+    .video_codec       = AV_CODEC_ID_VP8,
+    .write_header      = mkv_write_header,
+    .write_packet      = mkv_write_packet,
+    .write_trailer     = mkv_write_trailer,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
+                         AVFMT_TS_NONSTRICT,
+};
+#endif
+
+#if CONFIG_MATROSKA_AUDIO_MUXER
+AVOutputFormat ff_matroska_audio_muxer = {
+    .name              = "matroska",
+    .long_name         = NULL_IF_CONFIG_SMALL("Matroska"),
+    .mime_type         = "audio/x-matroska",
+    .extensions        = "mka",
+    .priv_data_size    = sizeof(MatroskaMuxContext),
+    .audio_codec       = CONFIG_LIBVORBIS_ENCODER ?
+                         AV_CODEC_ID_VORBIS : AV_CODEC_ID_AC3,
+    .video_codec       = AV_CODEC_ID_NONE,
+    .write_header      = mkv_write_header,
+    .write_packet      = mkv_write_packet,
+    .write_trailer     = mkv_write_trailer,
+    .flags             = AVFMT_GLOBALHEADER | AVFMT_TS_NONSTRICT,
+    .codec_tag         = (const AVCodecTag* const []){
+        ff_codec_wav_tags, additional_audio_tags, 0
+    },
+};
+#endif