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-rw-r--r--Changelog1
-rw-r--r--doc/muxers.texi21
-rw-r--r--libavformat/matroskaenc.c64
-rw-r--r--libavformat/version.h2
4 files changed, 86 insertions, 2 deletions
diff --git a/Changelog b/Changelog
index c3d84b3b5f..ab17dc62f6 100644
--- a/Changelog
+++ b/Changelog
@@ -37,6 +37,7 @@ version <next>:
- trim and atrim filters
- ffmpeg -t and -ss (output-only) options are now sample-accurate when
transcoding audio
+- Matroska muxer can now put the index at the beginning of the file.
version 1.2:
diff --git a/doc/muxers.texi b/doc/muxers.texi
index f1274948f8..dc627dc968 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -489,6 +489,27 @@ For example a 3D WebM clip can be created using the following command line:
ffmpeg -i sample_left_right_clip.mpg -an -c:v libvpx -metadata stereo_mode=left_right -y stereo_clip.webm
@end example
+This muxer supports the following options:
+
+@table @option
+
+@item reserve_index_space
+By default, this muxer writes the index for seeking (called cues in Matroska
+terms) at the end of the file, because it cannot know in advance how much space
+to leave for the index at the beginning of the file. However for some use cases
+-- e.g. streaming where seeking is possible but slow -- it is useful to put the
+index at the beginning of the file.
+
+If this option is set to a non-zero value, the muxer will reserve a given amount
+of space in the file header and then try to write the cues there when the muxing
+finishes. If the available space does not suffice, muxing will fail. A safe size
+for most use cases should be about 50kB per hour of video.
+
+Note that cues are only written if the output is seekable and this option will
+have no effect if it is not.
+
+@end table
+
@section segment, stream_segment, ssegment
Basic stream segmenter.
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 1f1ff49ece..da34ea7677 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -34,6 +34,7 @@
#include "libavutil/intreadwrite.h"
#include "libavutil/lfg.h"
#include "libavutil/mathematics.h"
+#include "libavutil/opt.h"
#include "libavutil/random_seed.h"
#include "libavutil/samplefmt.h"
#include "libavutil/sha.h"
@@ -81,6 +82,7 @@ typedef struct {
#define MODE_WEBM 0x02
typedef struct MatroskaMuxContext {
+ const AVClass *class;
int mode;
AVIOContext *dyn_bc;
ebml_master segment;
@@ -97,6 +99,9 @@ typedef struct MatroskaMuxContext {
AVPacket cur_audio_pkt;
int have_attachments;
+
+ int reserve_cues_space;
+ int64_t cues_pos;
} MatroskaMuxContext;
@@ -1042,6 +1047,11 @@ static int mkv_write_header(AVFormatContext *s)
if (mkv->cues == NULL)
return AVERROR(ENOMEM);
+ if (pb->seekable && mkv->reserve_cues_space) {
+ mkv->cues_pos = avio_tell(pb);
+ put_ebml_void(pb, mkv->reserve_cues_space);
+ }
+
av_init_packet(&mkv->cur_audio_pkt);
mkv->cur_audio_pkt.size = 0;
mkv->cluster_pos = -1;
@@ -1336,7 +1346,28 @@ static int mkv_write_trailer(AVFormatContext *s)
if (pb->seekable) {
if (mkv->cues->num_entries) {
- cuespos = mkv_write_cues(pb, mkv->cues, mkv->tracks, s->nb_streams);
+ if (mkv->reserve_cues_space) {
+ int64_t cues_end;
+
+ currentpos = avio_tell(pb);
+ avio_seek(pb, mkv->cues_pos, SEEK_SET);
+
+ cuespos = mkv_write_cues(pb, mkv->cues, mkv->tracks, s->nb_streams);
+ cues_end = avio_tell(pb);
+ if (cues_end > cuespos + mkv->reserve_cues_space) {
+ av_log(s, AV_LOG_ERROR, "Insufficient space reserved for cues: %d "
+ "(needed: %"PRId64").\n", mkv->reserve_cues_space,
+ cues_end - cuespos);
+ return AVERROR(EINVAL);
+ }
+
+ if (cues_end < cuespos + mkv->reserve_cues_space)
+ put_ebml_void(pb, mkv->reserve_cues_space - (cues_end - cuespos));
+
+ avio_seek(pb, currentpos, SEEK_SET);
+ } else {
+ 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;
@@ -1404,7 +1435,22 @@ const AVCodecTag additional_video_tags[] = {
{ AV_CODEC_ID_NONE, 0xFFFFFFFF }
};
+#define OFFSET(x) offsetof(MatroskaMuxContext, x)
+#define FLAGS AV_OPT_FLAG_ENCODING_PARAM
+static const AVOption options[] = {
+ { "reserve_index_space", "Reserve a given amount of space (in bytes) at the beginning "
+ "of the file for the index (cues).", OFFSET(reserve_cues_space), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
+ { NULL },
+};
+
#if CONFIG_MATROSKA_MUXER
+static const AVClass matroska_class = {
+ .class_name = "matroska muxer",
+ .item_name = av_default_item_name,
+ .option = options,
+ .version = LIBAVUTIL_VERSION_INT,
+};
+
AVOutputFormat ff_matroska_muxer = {
.name = "matroska",
.long_name = NULL_IF_CONFIG_SMALL("Matroska"),
@@ -1430,10 +1476,18 @@ AVOutputFormat ff_matroska_muxer = {
.subtitle_codec = AV_CODEC_ID_ASS,
#endif
.query_codec = mkv_query_codec,
+ .priv_class = &matroska_class,
};
#endif
#if CONFIG_WEBM_MUXER
+static const AVClass webm_class = {
+ .class_name = "webm muxer",
+ .item_name = av_default_item_name,
+ .option = options,
+ .version = LIBAVUTIL_VERSION_INT,
+};
+
AVOutputFormat ff_webm_muxer = {
.name = "webm",
.long_name = NULL_IF_CONFIG_SMALL("WebM"),
@@ -1447,10 +1501,17 @@ AVOutputFormat ff_webm_muxer = {
.write_trailer = mkv_write_trailer,
.flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
AVFMT_TS_NONSTRICT,
+ .priv_class = &webm_class,
};
#endif
#if CONFIG_MATROSKA_AUDIO_MUXER
+static const AVClass mka_class = {
+ .class_name = "matroska audio muxer",
+ .item_name = av_default_item_name,
+ .option = options,
+ .version = LIBAVUTIL_VERSION_INT,
+};
AVOutputFormat ff_matroska_audio_muxer = {
.name = "matroska",
.long_name = NULL_IF_CONFIG_SMALL("Matroska"),
@@ -1467,5 +1528,6 @@ AVOutputFormat ff_matroska_audio_muxer = {
.codec_tag = (const AVCodecTag* const []){
ff_codec_wav_tags, additional_audio_tags, 0
},
+ .priv_class = &mka_class,
};
#endif
diff --git a/libavformat/version.h b/libavformat/version.h
index 3e186a9e02..4666640d02 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -31,7 +31,7 @@
#define LIBAVFORMAT_VERSION_MAJOR 55
#define LIBAVFORMAT_VERSION_MINOR 4
-#define LIBAVFORMAT_VERSION_MICRO 100
+#define LIBAVFORMAT_VERSION_MICRO 101
#define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
LIBAVFORMAT_VERSION_MINOR, \
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-26 11:50:04 +0000