[FFmpeg-devel] [PATCH 2/2] Skip last samples in frame if needed

[Mashiat Sarker Shakkhar]

On 5/2/2012 11:59 PM, Jakub Stachowski wrote:
> ---
>   libavcodec/wmalosslessdec.c |   15 ++++++++++++++-
>   1 files changed, 14 insertions(+), 1 deletions(-)
>
> diff --git a/libavcodec/wmalosslessdec.c b/libavcodec/wmalosslessdec.c
> index c1e5480..b77d576 100644
> --- a/libavcodec/wmalosslessdec.c
> +++ b/libavcodec/wmalosslessdec.c
> @@ -977,8 +977,16 @@ static int decode_subframe(WmallDecodeCtx *s)
>
>       /* Write to proper output buffer depending on bit-depth */
>       for (i = 0; i<  s->channels_for_cur_subframe; i++) {
> +        int already_written;
>           int c = s->channel_indexes_for_cur_subframe[i];
> -        int subframe_len = s->channel[c].subframe_len[s->channel[c].cur_subframe];
> +
> +        if (s->bits_per_sample == 16)
> +            already_written = (s->samples_16[c] - ((int16_t *)s->frame.data[0] + c)) / s->num_channels;
> +        else
> +            already_written = (s->samples_32[c] - ((int32_t *)s->frame.data[0] + c)) / s->num_channels;
> +
> +        int subframe_len = FFMIN(s->frame.nb_samples - already_written, s->channel[c].subframe_len[s->channel[c].cur_subframe]);
> +

I am doubtful about this part, especially the way you calculate the 
number of samples already written. That's all I can say. Please try to 
get expert opinion from someone who know WMA / ASF.

>
>           for (j = 0; j<  subframe_len; j++) {
>               if (s->bits_per_sample == 16) {
> @@ -1056,6 +1064,11 @@ static int decode_frame(WmallDecodeCtx *s)
>           if (get_bits1(gb)) {
>               skip = get_bits(gb, av_log2(s->samples_per_frame * 2));
>               av_dlog(s->avctx, "end skip: %i\n", skip);
> +            s->frame.nb_samples -= skip;
> +            if (s->frame.nb_samples<0) {

As I have said before, one space each before and after operator is 
recommended.

> +                av_log(s->avctx, AV_LOG_ERROR,"negative number of samples\n");

I don't think this error message is accurate. After all, there's no such 
thing as "negative number of samples". A more accurate error messege 
IMHO would be something like - "Invalid value for end skip (Corrupted 
input?)". Others might disagree though.

Also we recommend a space after every comma.

> +                return AVERROR_INVALIDDATA;
> +           }
>           }
>
>       }

Regards
Shakkhar