[FFmpeg-devel] [PATCH 1/3] omadec: fix overflows during bit rate calculation

[Andreas Cadhalpun]

On 13.12.2016 08:11, Paul B Mahol wrote:
> On 12/13/16, Andreas Cadhalpun <andreas.cadhalpun at googlemail.com> wrote:
>> Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
>> ---
>>  libavformat/omadec.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavformat/omadec.c b/libavformat/omadec.c
>> index 6e476db..e7751d0 100644
>> --- a/libavformat/omadec.c
>> +++ b/libavformat/omadec.c
>> @@ -365,7 +365,7 @@ static int oma_read_header(AVFormatContext *s)
>>          st->codecpar->channels    = 2;
>>          st->codecpar->channel_layout = AV_CH_LAYOUT_STEREO;
>>          st->codecpar->sample_rate = samplerate;
>> -        st->codecpar->bit_rate    = st->codecpar->sample_rate * framesize *
>> 8 / 1024;
>> +        st->codecpar->bit_rate    = st->codecpar->sample_rate * framesize /
>> 128;
>>
>>          /* fake the ATRAC3 extradata
>>           * (wav format, makes stream copy to wav work) */
>> @@ -398,7 +398,7 @@ static int oma_read_header(AVFormatContext *s)
>>              return AVERROR_INVALIDDATA;
>>          }
>>          st->codecpar->sample_rate = samplerate;
>> -        st->codecpar->bit_rate    = samplerate * framesize * 8 / 2048;
>> +        st->codecpar->bit_rate    = samplerate * framesize / 256;
>>          avpriv_set_pts_info(st, 64, 1, samplerate);
>>          break;
>>      case OMA_CODECID_MP3:
> 
> Shouldn't using 8LL or similar be more future-proof?

Why multiply with 8 when dividing by a multiple of 8 directly afterwards?
That's just a waste of computational resources.
If sample_rate and/or framesize get larger in the future, a cast can be added.

Best regards,
Andreas