[FFmpeg-devel] [PATCH] als in mp4

[Baptiste Coudurier]

Hi Jai,

On 4/6/2009 5:12 AM, Jai Menon wrote:
> On Fri, Apr 3, 2009 at 11:28 PM, Baptiste Coudurier
>
> [...]
> 
> 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;
> @@ -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;
> +    }

There is something I don't understand according to the code above,
position might not be fixed depending on several conditions.

How can you read at fixed position in "buf" ?
It would depends on what has been read.

Futhermore, I don't get why ALS does not use correctly sample rate like
others AOT. Can you please explain/quote specs ?

[...]

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
checking for life_signs in -lkenny... no
FFmpeg maintainer                                  http://www.ffmpeg.org