[FFmpeg-devel] [PATCH] avcodec/snowdec: Check intra block dc differences.

[James Almer]

On 9/4/2017 11:00 PM, Ronald S. Bultje wrote:
> Hi,
> 
> On Mon, Sep 4, 2017 at 12:11 PM, Michael Niedermayer <michael at niedermayer.cc
>> wrote:
> 
>>          if(type){
>> +            int ld, cbd, crd;
>>              pred_mv(s, &mx, &my, 0, left, top, tr);
>> -            l += get_symbol(&s->c, &s->block_state[32], 1);
>> +            ld = get_symbol(&s->c, &s->block_state[32], 1);
>> +            if (ld < -255 || ld > 255) {
>> +                av_log(s->avctx, AV_LOG_ERROR, "Invalid (Out of range)
>> intra luma block DC difference %d\n", ld);
>> +                return AVERROR_INVALIDDATA;
>> +            }
>> +            l += ld;
>>              if (s->nb_planes > 2) {
>> -                cb+= get_symbol(&s->c, &s->block_state[64], 1);
>> -                cr+= get_symbol(&s->c, &s->block_state[96], 1);
>> +                cbd = get_symbol(&s->c, &s->block_state[64], 1);
>> +                crd = get_symbol(&s->c, &s->block_state[96], 1);
>> +                if (cbd < -255 || cbd > 255 || crd < -255 || crd > 255) {
>> +                    av_log(s->avctx, AV_LOG_ERROR, "Invalid (Out of
>> range) intra chroma block DC difference %d, %d\n", cbd, crd);
>> +                    return AVERROR_INVALIDDATA;
>> +                }
>> +                cb += cbd;
>> +                cr += crd;
>>              }
> 
> 
> I recognize the great improvements in your messages. They are much better
> than before. They are still not appropriate for display to end users.
> Please use ff_tlog(), as was suggested in the original thread.

Now that i looked at ff_tlog() closely it's only enabled if -DTRACE is
used during compilation, and then it prints stuff at the trace log
level, which is even lower than debug and used to print a bunch of
assorted values that are not error log messages.
The chances for a dev to ever use that is very low outside of very
specific cases, seeing that even a sane h264 clip will trash the
terminal with an endless amount of log lines.

So if anything, use debug level instead of error in the av_log call.