On Tue, 31 Jan 2017 12:02:01 -0800 Chris Cunningham <chcunning...@chromium.org> wrote:
> Thanks for taking a look. > > Definitely missing a "break;" - will fix in subsequent patch. > > Agree timestamps should be relative (didn't realize this). Vignesh points > out that "0" in the test file is due to a bug in ffmpeg (and probably other > muxers) where this value is not written as a relative timestamp, but > instead as the timestamp of the previous frame. https://github.com/FFmp > eg/FFmpeg/blob/master/libavformat/matroskaenc.c#L2053 > <https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2FFFmpeg%2FFFmpeg%2Fblob%2Fmaster%2Flibavformat%2Fmatroskaenc.c%23L2053&sa=D&sntz=1&usg=AFQjCNGs8m6GsWbhTvCZl0Q_juGAldQblA> Just a few lines below this reads mkv->last_track_timestamp[track_number - 1] = ts - mkv->cluster_pts; which looks like it intends to write a relative value. Though "ts" can be a DTS, while the other value is always a PTS. > Anyway, I'm all for following Haali. Its not obvious how best to do this. I > don't think there's any great default value to indicate "not-set" and the > generic embl parsing code that reads the reference timestamp doesn't really > lend itself to setting an additional field like > MatroskaBlock.has_reference. I can sort this out, but I'll pause in case > you have a recommendation in-mind. I don't know a nice way either. Here are 3 potential ways I came up with: 1. Use a better dummy value, like INT64_MIN, which is almost 100% unlikely to appear in a valid file. (This is probably equivalent to your intention in original patch.) 2. Add a new "presence_flag_offset" field to EbmlSyntax - the EBML reader will write a 1 to it if the element was found. (This is a bit annoying, because 0 is a valid offset, and you surely wouldn't want to change all the other element definitions.) 3. Add a new type like EBML_PRESENCE, which writes whether the element was present or not to data_offset, instead of the element's content or its default value. (There are some other special "types" like EBML_STOP, so maybe this idea isn't all too hacky.) _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
