[FFmpeg-devel] [PATCH 4/8] avcodec/g728dec: G.728 decoder

[James Almer]

On 1/11/2025 11:37 PM, Peter Ross wrote:
> ---
>   libavcodec/Makefile     |   1 +
>   libavcodec/allcodecs.c  |   1 +
>   libavcodec/codec_desc.c |   7 ++
>   libavcodec/codec_id.h   |   1 +
>   libavcodec/g728data.h   |  70 +++++++++++++
>   libavcodec/g728dec.c    | 213 ++++++++++++++++++++++++++++++++++++++++
>   libavcodec/utils.c      |   1 +
>   7 files changed, 294 insertions(+)
>   create mode 100644 libavcodec/g728data.h
>   create mode 100644 libavcodec/g728dec.c

[...]

> +
> +static int g728_decode_frame(AVCodecContext *avctx, AVFrame *frame,
> +                            int *got_frame_ptr, AVPacket *avpkt)
> +{
> +    G728Context *s = avctx->priv_data;
> +    GetBitContext gb;
> +    int ret;
> +
> +    if (avpkt->size < 5)
> +        return AVERROR_INVALIDDATA;
> +
> +    if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
> +        return ret;
> +
> +    frame->nb_samples = 20;
> +    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
> +        return ret;
> +
> +    decode_frame(s, &gb, (float *)frame->data[0]);

I assume this means the codec is mono only, right? I see you set 
AV_CODEC_CAP_CHANNEL_CONF below (meaning the decoder will set channel 
information and not depend on the caller doing it), but then don't force 
mono layout in avctx->ch_layout anywhere.
You need to do it in g728_decode_init(), first uninitializing the 
existing layout and then setting it to mono.

> +
> +    *got_frame_ptr = 1;
> +
> +    return 5;
> +}
> +
> +const FFCodec ff_g728_decoder = {
> +    .p.name         = "g728",
> +    CODEC_LONG_NAME("G.728)"),
> +    .p.type         = AVMEDIA_TYPE_AUDIO,
> +    .p.id           = AV_CODEC_ID_G728,
> +    .priv_data_size = sizeof(G728Context),
> +    .init           = g728_decode_init,
> +    .close          = g728_decode_close,
> +    FF_CODEC_DECODE_CB(g728_decode_frame),
> +    .p.capabilities = AV_CODEC_CAP_CHANNEL_CONF |
> +                      AV_CODEC_CAP_DR1,
> +    .p.sample_fmts  = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLT,
> +                                                      AV_SAMPLE_FMT_NONE },
> +};
> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> index dd846b4ae9..58b29c4c9d 100644
> --- a/libavcodec/utils.c
> +++ b/libavcodec/utils.c
> @@ -553,6 +553,7 @@ int av_get_bits_per_sample(enum AVCodecID codec_id)
>       case AV_CODEC_ID_DFPWM:
>           return 1;
>       case AV_CODEC_ID_ADPCM_SBPRO_2:
> +    case AV_CODEC_ID_G728:
>           return 2;
>       case AV_CODEC_ID_ADPCM_SBPRO_3:
>           return 3;
> 
> 
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