[FFmpeg-devel] [PATCH] als in mp4

[Jai Menon]

On 3/23/09, Alex Converse <alex.converse at gmail.com> wrote:
> On Mon, Mar 23, 2009 at 12:11 AM, Jai Menon <jmenon86 at gmail.com> wrote:
>  > On 3/21/09, Alex Converse <alex.converse at gmail.com> wrote:
>  >> On Sat, Mar 21, 2009 at 1:50 AM, Jai Menon <jmenon86 at gmail.com> wrote:
>  >>  >
>  >>  > Hi,
>  >>  >
>  >>  > Attached :
>  >>  >
>  >>  > 1) demux als streams from mp4, als codec id and minor lavc version bump
>  >>  > 2) mux als in to mp4, add isomedia type
>  >>  >
>  >>  > --
>  >>  > Regards,
>  >>  >
>  >>  > Jai
>  >>  >
>  >>
>  >> > _______________________________________________
>  >>  > ffmpeg-devel mailing list
>  >>  > ffmpeg-devel at mplayerhq.hu
>  >>  > https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel
>  >>
>  >>
>  >> > Index: libavformat/mov.c
>  >>  > ===================================================================
>  >>  > --- libavformat/mov.c    (revision 18065)
>  >>  > +++ libavformat/mov.c    (working copy)
>  >>  > @@ -426,6 +426,11 @@
>  >>  >                                           st->codec->extradata_size);
>  >>  >                  if (cfg.chan_config > 7)
>  >>  >                      return -1;
>  >>  > +                if(cfg.object_type == 36) {
>  >>
>  >> > +                    st->codec->codec_id = CODEC_ID_MP4ALS;
>  >>  > +                    st->codec->codec_type = CODEC_TYPE_AUDIO;
>  >>
>  >> > +                    return 0;
>  >>  > +                }
>  >>  >                  st->codec->channels = ff_mpeg4audio_channels[cfg.chan_config];
>  >>  >                 if (cfg.object_type == 29 && cfg.sampling_index < 3) // old mp3on4
>  >>  >                     st->codec->sample_rate = ff_mpa_freq_tab[cfg.sampling_index];
>  >>
>  >>
>  >> I hope this isn't too bikeshedy but can this be made part of the
>  >>  codec_get_id section below.
>  >
>  > It can and it should be. But as i said, the reference codec does not
>  > write the channel config correctly. So some if(codec_id != MP4ALS)
>  > will still be required. So it will still look like a hack ;)
>  >
>
>
> Do you mean it's incorrect or do you mean it's set to zero? AAC still
>  works fine when it's set to zero.

It's set to zero, which i think implies that the value should be read
from als specifc config (what i understood from the spec). But as of
now, the code doesn't check if any of the values read from the audio
config object are zero, instead, it just overwrites the values which
were set initially in the codec context (and which happened to be
correct).

>  Also if you do end up trying to match AOT numbers please try to use
>  the enum from mpeg4audio.h. ALS's name in the enum is AOT_ALS.

A later patch i posted used these. I didn't know they existed because
i was working from an old checkout.

[...]

-- 
Regards,

Jai