[FFmpeg-devel,1/5] avcodec/adpcm_ima_amv: restrict to 1 channel

The format doesn't allow for anything else.

Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>
---
 libavcodec/adpcm.c | 5 ++++-
 libavcodec/utils.c | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

Zane van Iperen:
> The format doesn't allow for anything else.
> 
> Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>
> ---
>  libavcodec/adpcm.c | 5 ++++-
>  libavcodec/utils.c | 2 +-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
> index 701b125c47..d34fd6c6e1 100644
> --- a/libavcodec/adpcm.c
> +++ b/libavcodec/adpcm.c
> @@ -110,6 +110,7 @@ static av_cold int adpcm_decode_init(AVCodecContext * avctx)
>      unsigned int max_channels = 2;
>  
>      switch(avctx->codec->id) {
> +    case AV_CODEC_ID_ADPCM_IMA_AMV:
>      case AV_CODEC_ID_ADPCM_IMA_CUNNING:
>          max_channels = 1;
>          break;
> @@ -1684,6 +1685,8 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data,
>          }
>          break;
>      case AV_CODEC_ID_ADPCM_IMA_AMV:
> +        av_assert0(avctx->channels == 1);
> +

Which check ensures that this assert won't be triggered?

>          c->status[0].predictor = sign_extend(bytestream2_get_le16u(&gb), 16);
>          c->status[0].step_index = bytestream2_get_byteu(&gb);
>          bytestream2_skipu(&gb, 5);
> @@ -1693,7 +1696,7 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data,
>              return AVERROR_INVALIDDATA;
>          }
>  
> -        for (n = nb_samples >> (1 - st); n > 0; n--) {
> +        for (n = nb_samples >> 1; n > 0; n--) {
>              int v = bytestream2_get_byteu(&gb);
>  
>              *samples++ = adpcm_ima_expand_nibble(&c->status[0], v >> 4, 3);
> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> index 110496cc44..71d51ddad6 100644
> --- a/libavcodec/utils.c
> +++ b/libavcodec/utils.c
> @@ -1695,7 +1695,7 @@ static int get_audio_frame_duration(enum AVCodecID id, int sr, int ch, int ba,
>              case AV_CODEC_ID_ADPCM_IMA_SMJPEG:
>                  return (frame_bytes - 4) * 2 / ch;
>              case AV_CODEC_ID_ADPCM_IMA_AMV:
> -                return (frame_bytes - 8) * 2 / ch;
> +                return (frame_bytes - 8) * 2;
>              case AV_CODEC_ID_ADPCM_THP:
>              case AV_CODEC_ID_ADPCM_THP_LE:
>                  if (extradata)
>

On 2/11/20 7:48 pm, Andreas Rheinhardt wrote:
> 
> Zane van Iperen:
>> The format doesn't allow for anything else.
>>
>> Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>
>> ---
>>   libavcodec/adpcm.c | 5 ++++-
>>   libavcodec/utils.c | 2 +-
>>   2 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
>> index 701b125c47..d34fd6c6e1 100644
>> --- a/libavcodec/adpcm.c
>> +++ b/libavcodec/adpcm.c
>> @@ -110,6 +110,7 @@ static av_cold int adpcm_decode_init(AVCodecContext * avctx)
>>       unsigned int max_channels = 2;
>>
>>       switch(avctx->codec->id) {
>> +    case AV_CODEC_ID_ADPCM_IMA_AMV:
>>       case AV_CODEC_ID_ADPCM_IMA_CUNNING:
>>           max_channels = 1;
>>           break;
>> @@ -1684,6 +1685,8 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data,
>>           }
>>           break;
>>       case AV_CODEC_ID_ADPCM_IMA_AMV:
>> +        av_assert0(avctx->channels == 1);
>> +
> 
> Which check ensures that this assert won't be triggered?
> 

At the very top of the patch, just above "case 
AV_CODEC_ID_ADPCM_IMA_CUNNING:".
max_channels is set to 1, so it'll bail before it gets to the assert.