[FFmpeg-devel] [PATCH] als in mp4

[Robert Swain]

On 6/4/09 13:12, Jai Menon wrote:
> On Fri, Apr 3, 2009 at 11:28 PM, Baptiste Coudurier
> <baptiste.coudurier at gmail.com>  wrote:

[snip]

>> >  I think the AOT_ALS case should be handled within mpeg4audio_get_config,
>> >  to retrieve correct sample_rate/channels if these are not set in
>> >  AudioSpecificCOnfig, I also beleve all AOT should be handled this way.
>
> another attempt.

[snip]

> diff --git a/libavcodec/mpeg4audio.c b/libavcodec/mpeg4audio.c
> index 9c7e02b..b391609 100644
> --- a/libavcodec/mpeg4audio.c
> +++ b/libavcodec/mpeg4audio.c
> @@ -55,6 +55,8 @@ int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_si
>       c->object_type = get_object_type(&gb);
>       c->sample_rate = get_sample_rate(&gb,&c->sampling_index);
>       c->chan_config = get_bits(&gb, 4);
> +    c->absolute_channels = 0;
> +    c->bits_per_sample   = 0;
>       c->sbr = -1;
>       if (c->object_type == 5) {
>           c->ext_object_type = c->object_type;

We should swap these constants out for AOT_SBR and so on as appropriate 
in my opinion. But this isn't your job. :)

> @@ -80,5 +82,11 @@ int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_si
>                   get_bits1(&gb); // skip 1 bit
>           }
>       }
> +    if (c->object_type == AOT_ALS) {
> +        c->absolute_channels = 1;
> +        c->sample_rate       = AV_RB32(buf + 10);
> +        c->chan_config       = AV_RB16(buf + 18) + 1;
> +        c->bits_per_sample   = (((buf[20]>>  2)&  0x07) + 1)<<  3;
> +    }
>       return specific_config_bitindex;
>   }

I expect this to be a switch in future, but for the moment the if () is 
fine in my opinion.

> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 214e74e..0020358 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -425,13 +425,18 @@ static int mov_read_esds(MOVContext *c, ByteIOContext *pb, MOVAtom atom)
>                   MPEG4AudioConfig cfg;
>                   ff_mpeg4audio_get_config(&cfg, st->codec->extradata,
>                                            st->codec->extradata_size);
> +                if (!cfg.absolute_channels) {
>                   if (cfg.chan_config>  7)
>                       return -1;
>                   st->codec->channels = ff_mpeg4audio_channels[cfg.chan_config];
> +                } else st->codec->channels = cfg.chan_config;
> +

Nit:

                 } else
                     st->codec->channels = cfg.chan_config;

Looks OK to me but wait for Baptiste to comment as he is the maintainer 
of this code.

Regards,
Rob