Based on my understanding of [1], these values in the Info tag specify only the encoder delay/padding, which matches the documentation for these fields. It looks like other formats are using the fields that way as well.
I think the extra 528 + 1 samples are the decoder delay [2]. It looks like libmp3lame adds the 528 + 1 only to have mp3dec subtract it, so I'm not sure why that's done. IIUC start_skip_samples is the mechanism that actually accounts for the extra delay when decoding. [1]: http://gabriel.mp3-tech.org/mp3infotag.html#delays [2]: http://lame.sourceforge.net/tech-FAQ.txt Jon Toohill | Google Play Music | jtooh...@google.com | (650) 215-0770 On Thu, May 26, 2016 at 7:51 PM, Michael Niedermayer <mich...@niedermayer.cc > wrote: > On Wed, May 25, 2016 at 09:56:59AM -0700, Jon Toohill wrote: > > --- > > libavformat/mp3dec.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c > > index 3725d67..192f5ef 100644 > > --- a/libavformat/mp3dec.c > > +++ b/libavformat/mp3dec.c > > @@ -234,6 +234,8 @@ static void mp3_parse_info_tag(AVFormatContext *s, > AVStream *st, > > > > mp3->start_pad = v>>12; > > mp3-> end_pad = v&4095; > > + st->codecpar->initial_padding = mp3->start_pad; > > + st->codecpar->trailing_padding = mp3->end_pad; > > st->start_skip_samples = mp3->start_pad + 528 + 1; > > if (mp3->frames) { > > st->first_discard_sample = -mp3->end_pad + 528 + 1 + > mp3->frames * (int64_t)spf; > > is the 528 + 1 difference intended to > start_skip_samples/first_discard_sample > ? > mp3enc stores par->initial_padding - 528 - 1 > > [...] > > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > If you drop bombs on a foreign country and kill a hundred thousand > innocent people, expect your government to call the consequence > "unprovoked inhuman terrorist attacks" and use it to justify dropping > more bombs and killing more people. The technology changed, the idea is > old. > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
