[FFmpeg-devel] [PATCH] avcodec/libmp3lame: properly handle unaligned frame data

[Muhammad Faiz]

On Wed, Apr 26, 2017 at 5:34 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Wed, 26 Apr 2017 17:16:05 +0700
> Muhammad Faiz <mfcc64 at gmail.com> wrote:
>
>> This should fix Ticket6349
>>
>> Since 383057f8e744efeaaa3648a59bc577b25b055835, framequeue may
>> generate unaligned frame data.
>>
>> Signed-off-by: Muhammad Faiz <mfcc64 at gmail.com>
>> ---
>>  libavcodec/libmp3lame.c | 13 +++++++++----
>>  1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/libavcodec/libmp3lame.c b/libavcodec/libmp3lame.c
>> index 5e26743..cd505bb 100644
>> --- a/libavcodec/libmp3lame.c
>> +++ b/libavcodec/libmp3lame.c
>> @@ -203,15 +203,20 @@ static int mp3lame_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
>>              ENCODE_BUFFER(lame_encode_buffer_int, int32_t, frame->data);
>>              break;
>>          case AV_SAMPLE_FMT_FLTP:
>> -            if (frame->linesize[0] < 4 * FFALIGN(frame->nb_samples, 8)) {
>> -                av_log(avctx, AV_LOG_ERROR, "inadequate AVFrame plane padding\n");
>> -                return AVERROR(EINVAL);
>> -            }
>>              for (ch = 0; ch < avctx->channels; ch++) {
>> +                if (frame->linesize[0] < 4 * FFALIGN(frame->nb_samples, 8) || 0x1F & (intptr_t)(frame->data[ch])) {
>> +                    float *src = (float *) frame->data[ch];
>> +                    float *dst = s->samples_flt[ch];
>> +                    int k;
>> +
>> +                    for (k = 0; k < frame->nb_samples; k++)
>> +                        dst[k] = src[k] * 32768.0f;
>> +                } else {
>>                  s->fdsp->vector_fmul_scalar(s->samples_flt[ch],
>>                                             (const float *)frame->data[ch],
>>                                             32768.0f,
>>                                             FFALIGN(frame->nb_samples, 8));
>> +                }
>>              }
>>              ENCODE_BUFFER(lame_encode_buffer_float, float, s->samples_flt);
>>              break;
>
> Looks like the right solution is fixing framequeue.
>
> I don't think encoders generally allow lax alignment, and this might
> not be the only case.

This requirement is not documented. Also some filters may also
generate unaligned data, for example crop filter.