Re: [FFmpeg-devel] [PATCHv3 7/8] avformat/aiff: G.728 muxing and demuxing

From: compn <ff@hawaiiantel.net>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCHv3 7/8] avformat/aiff: G.728 muxing and demuxing
Date: Mon, 9 Jun 2025 14:07:07 -1000
Message-ID: <20250609140707.00002838@hawaiiantel.net> (raw)
In-Reply-To: <GV1P250MB0737B292BE5B0EFE4C64BA4D8F6BA@GV1P250MB0737.EURP250.PROD.OUTLOOK.COM>

On Tue, 10 Jun 2025 00:25:24 +0200, Andreas Rheinhardt wrote:

> Peter Ross:
> > ---
> >  libavformat/aiff.c    | 1 +
> >  libavformat/aiffdec.c | 3 +++
> >  2 files changed, 4 insertions(+)
> > 
> > diff --git a/libavformat/aiff.c b/libavformat/aiff.c
> > index 1ceac69a70..907f7d8d28 100644
> > --- a/libavformat/aiff.c
> > +++ b/libavformat/aiff.c
> > @@ -40,6 +40,7 @@ const AVCodecTag ff_codec_aiff_tags[] = {
> >      { AV_CODEC_ID_GSM,          MKTAG('G','S','M',' ') },
> >      { AV_CODEC_ID_ADPCM_G722,   MKTAG('G','7','2','2') },
> >      { AV_CODEC_ID_ADPCM_G726LE, MKTAG('G','7','2','6') },
> > +    { AV_CODEC_ID_G728,         MKTAG('G','7','2','8') },
> >      { AV_CODEC_ID_PCM_S16BE,    MKTAG('t','w','o','s') },
> >      { AV_CODEC_ID_PCM_S16LE,    MKTAG('s','o','w','t') },
> >      { AV_CODEC_ID_ADPCM_IMA_QT, MKTAG('i','m','a','4') },
> > diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
> > index bd5bd2e4bb..aeb00cccd0 100644
> > --- a/libavformat/aiffdec.c
> > +++ b/libavformat/aiffdec.c
> > @@ -174,6 +174,9 @@ static int get_aiff_header(AVFormatContext *s, int64_t size,
> >          case AV_CODEC_ID_GSM:
> >              par->block_align = 33;
> >              break;
> > +        case AV_CODEC_ID_G728:
> > +            par->block_align = 5;
> > +            break;
> >          default:
> >              aiff->block_duration = 1;
> >              break;
> >   
> Is this and the riff patch based on some spec or are you just inventing
> things here?

maybe i can help.

https://wiki.multimedia.cx/index.php/G.728
lists 0xCD02 and 0x0041
according to the history of that wiki page, the 0xCD02 comes from
"plcmg728.acm" binary codec.

other list of twocc here: https://wiki.multimedia.cx/index.php/TwoCC

i havent myself tested plcmg728.acm , but its on my list to investigate
here https://wiki.multimedia.cx/index.php/Category_talk:Audio_Codecs

plcmg728.acm should be included with the software:
Polycom PVX
"Create video conferences with a USB webcam"

did Polycom make up that entry or should we support it anyways? i say
support it until another 0xCD02 shows up. and then we deal with the
conflict at that time.

if you go to the spec page
https://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AIFF/AIFF.html
and click samples
https://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AIFF/Samples.html
at the bottom is g728 sample
 o2_728.aiff (1 kB) *
    AIFF-C file: G.728 data (compression code: G728)

hopefully that answers all riff/aiff questions.

-compn
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