| Message ID | CAPgnUfCmx-=6zEaxM3a8GUEp9x2RH3+q3tnrsOuko1VNgw=3dA@mail.gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
2018-09-05 22:52 GMT+02:00, Sigríður Regína Sigurþórsdóttir <siggaregina@gmail.com>: > --- > Changelog | 1 + > doc/muxers.texi | 4 ++++ > libavformat/matroskaenc.c | 8 ++++++++ > 3 files changed, 13 insertions(+) > > diff --git a/Changelog b/Changelog > index 0975fee..689b04c 100644 > --- a/Changelog > +++ b/Changelog > @@ -21,6 +21,7 @@ version <next>: > - Brooktree ProSumer video decoder > - MatchWare Screen Capture Codec decoder > - WinCam Motion Video decoder > +- Matroska muxer has optional free space for unspecified use at the > beginning of the file. No need for a Changelog entry. In which situation is the new option useful? Carl Eugen
On 9/5/2018 6:36 PM, Carl Eugen Hoyos wrote: > 2018-09-05 22:52 GMT+02:00, Sigríður Regína Sigurþórsdóttir > <siggaregina@gmail.com>: >> --- >> Changelog | 1 + >> doc/muxers.texi | 4 ++++ >> libavformat/matroskaenc.c | 8 ++++++++ >> 3 files changed, 13 insertions(+) >> >> diff --git a/Changelog b/Changelog >> index 0975fee..689b04c 100644 >> --- a/Changelog >> +++ b/Changelog >> @@ -21,6 +21,7 @@ version <next>: >> - Brooktree ProSumer video decoder >> - MatchWare Screen Capture Codec decoder >> - WinCam Motion Video decoder >> +- Matroska muxer has optional free space for unspecified use at the >> beginning of the file. > > No need for a Changelog entry. > > In which situation is the new option useful? Adding a bunch of reserved filler bytes is something done by a lot of writing applications and meant to be used mainly by retagging applications to add or replace tags in place without the risk of having to rewrite the entire file. Hence it being added right after the Tags element. Mkvtoolnix adds a big Void element for this purpose by default, for example. But for libavformat I'd rather have this be optional. > > Carl Eugen > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel >
On 2018-09-05 22:52, Sigríður Regína Sigurþórsdóttir wrote: > + {"reserve_free_space", "Reserve a given amount of space at the > beginning og the file for unspecified purpose." I added the "metadata_header_padding" global option many years ago. Can you not reuse it for this purpose? Is it not likely to be "metadata" that another software might fill this with? Also there is a typo in the bit I quoted.
diff --git a/Changelog b/Changelog index 0975fee..689b04c 100644 --- a/Changelog +++ b/Changelog @@ -21,6 +21,7 @@ version <next>: - Brooktree ProSumer video decoder - MatchWare Screen Capture Codec decoder - WinCam Motion Video decoder +- Matroska muxer has optional free space for unspecified use at the beginning of the file. version 4.0: diff --git a/doc/muxers.texi b/doc/muxers.texi index f18543e..72da90e 100644 --- a/doc/muxers.texi +++ b/doc/muxers.texi @@ -1213,6 +1213,10 @@ ffmpeg -i sample_left_right_clip.mpg -an -c:v libvpx -metadata stereo_mode=left_ This muxer supports the following options: @table @option + +@item reserve_free_space +Reserve the specified amount of bytes for unspecified purpose within the file header. + @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 diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c index 09a62e1..2eb65f8 100644 --- a/libavformat/matroskaenc.c +++ b/libavformat/matroskaenc.c @@ -144,6 +144,7 @@ typedef struct MatroskaMuxContext { int have_attachments; int have_video; + int reserve_free_space; int reserve_cues_space; int cluster_size_limit; int64_t cues_pos; @@ -2005,6 +2006,12 @@ static int mkv_write_header(AVFormatContext *s) ret = AVERROR(ENOMEM); goto fail; } + if (mkv->reserve_free_space) { + if (mkv->reserve_free_space == 1) + mkv->reserve_free_space++; + put_ebml_void(pb, mkv->reserve_free_space); + } + if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && mkv->reserve_cues_space) { mkv->cues_pos = avio_tell(pb); if (mkv->reserve_cues_space == 1) @@ -2767,6 +2774,7 @@ static const AVCodecTag additional_subtitle_tags[] = { #define OFFSET(x) offsetof(MatroskaMuxContext, x) #define FLAGS AV_OPT_FLAG_ENCODING_PARAM static const AVOption options[] = { + {"reserve_free_space", "Reserve a given amount of space at the beginning og the file for unspecified purpose.", OFFSET(reserve_free_space), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, FLAGS },
--- Changelog | 1 + doc/muxers.texi | 4 ++++ libavformat/matroskaenc.c | 8 ++++++++ 3 files changed, 13 insertions(+) { "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 }, { "cluster_size_limit", "Store at most the provided amount of bytes in a cluster. ", OFFSET(cluster_size_limit), AV_OPT_TYPE_INT , { .i64 = -1 }, -1, INT_MAX, FLAGS }, { "cluster_time_limit", "Store at most the provided number of milliseconds in a cluster.", OFFSET(cluster_time_limit), AV_OPT_TYPE_INT64, { .i64 = -1 }, -1, INT64_MAX, FLAGS },