Michael et al., is this good to merge as-is? I just tested and a round trip with ffmpeg from wav -> mp3 -> wav retains the correct number of samples.
Jon Toohill | Google Play Music | jtooh...@google.com | (650) 215-0770 On Wed, Jun 1, 2016 at 5:58 PM, Jon Toohill <jtooh...@google.com> wrote: > 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
