[FFmpeg-devel] [PATCH] s302m: fix arithmetic exception

[Andreas Cadhalpun]

On 26.06.2015 01:27, Michael Niedermayer wrote:
> On Fri, Jun 26, 2015 at 12:05:09AM +0200, Andreas Cadhalpun wrote:
>> If 'buf_size * 8' is smaller than 'avctx->channels *
>> (avctx->bits_per_raw_sample + 4)' it resulted in a division by zero.
>>
>> Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
>> ---
>>  libavcodec/s302m.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavcodec/s302m.c b/libavcodec/s302m.c
>> index 5cf9eb5..36c8e7c 100644
>> --- a/libavcodec/s302m.c
>> +++ b/libavcodec/s302m.c
>> @@ -86,9 +86,9 @@ static int s302m_parse_frame_header(AVCodecContext *avctx, const uint8_t *buf,
>>              avctx->channel_layout = AV_CH_LAYOUT_5POINT1_BACK | AV_CH_LAYOUT_STEREO_DOWNMIX;
>>      }
>>      avctx->bit_rate    = 48000 * avctx->channels * (avctx->bits_per_raw_sample + 4) +
>> -                         32 * (48000 / (buf_size * 8 /
>> -                                        (avctx->channels *
>> -                                         (avctx->bits_per_raw_sample + 4))));
>> +                         32 * (48000 * avctx->channels
>> +                                * (avctx->bits_per_raw_sample + 4))
>> +                            / (buf_size * 8);
> 
> i dont think the new code matches the nb_samples vs. buf_size vs.
> samplerate of s302m_decode_frame()

I don't think the old code did either.

> maybe the nb_samples calculation could be factored out and used for
> bitrate computation too

It can just be reused, which also nicely avoids the division by zero.
New patch attached.

Best regards,
Andreas

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