[FFmpeg-devel] [PATCH] avcodec/videotoolboxenc: fix encoding frame crash on iOS 11

[sharp bai]

We have tested on iOS 12 and other version. Only on iOS 11 this crash occurs,
regardless using which device such as iPhone 8, iPhone X or iPhone 7.

Aman Gupta <ffmpeg at tmm1.net> 于2019年9月4日周三 上午7:48写道：
>
>
>
> On Mon, Aug 12, 2019 at 11:50 PM sharpbai <sharpbai at gmail.com> wrote:
>>
>> On iOS 11, encoding a frame may return error with log
>> "Error encoding frame 0", which means vtenc_output_callback
>> is called with status=0 and sample_buffer=NULL. Then the
>> encoding session will be crashed on next callback wether or not
>> closing the codec context.
>>
>> Let us look through the link below introducing VTCompressionOutputCallback,
>>
>> https://developer.apple.com/documentation/videotoolbox/vtcompressionoutputcallback?language=objc
>>
>> "status=0" (noErr) means compression was successful.
>> "sampleBuffer=NULL" means the frame was dropped when compression
>> was successful (status=0) or compression was not successful (status!=0).
>>
>> So we should not set AVERROR_EXTERNAL on "status=0" and "sample_buffer=NULL"
>> as it is not a error.
>>
>> The fix is that we only set AVERROR_EXTERNAL with status value non zero.
>> When sample_buffer is NULL and status value is zero, we simply return
>> with no other operation.
>>
>> This crash often occurs on iOS 11 for example encoding 720p at 25fps.
>
>
> Is it fixed in iOS 12, or untested there?
>
>>
>>
>> Signed-off-by: sharpbai <sharpbai at gmail.com>
>> ---
>>  libavcodec/videotoolboxenc.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/videotoolboxenc.c b/libavcodec/videotoolboxenc.c
>> index d76bb7f646..8afdd125d2 100644
>> --- a/libavcodec/videotoolboxenc.c
>> +++ b/libavcodec/videotoolboxenc.c
>> @@ -569,12 +569,16 @@ static void vtenc_output_callback(
>>          return;
>>      }
>>
>> -    if (status || !sample_buffer) {
>> +    if (status) {
>>          av_log(avctx, AV_LOG_ERROR, "Error encoding frame: %d\n", (int)status);
>>          set_async_error(vtctx, AVERROR_EXTERNAL);
>>          return;
>>      }
>>
>> +    if (!sample_buffer) {
>> +        return;
>> +    }
>> +
>>      if (!avctx->extradata && (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER)) {
>>          int set_status = set_extradata(avctx, sample_buffer);
>>          if (set_status) {
>> --
>> 2.21.0
>>
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-- 
Regards,

Sharpbai
Focus on web programming.

Blog - https://blog.sharpbai.com/