Ffmpeg possible sws_scale memory leak

Question

I'm decoding whatever the camera codec is and then always encode it to H264 and more specifically qsv if it is supported. Currently having 2 cameras to test. One is H264 encoding and one is rawvideo. The problem comes with rawvideo. The pixel format is BGR24 and scaling to NV12

I will simplify the code because it is as any other example.

avcodec_send_packet()
// while
avcodec_receive_frame()

// if frame is not EAGAIN convert BGR24 to NV12
if (_pConvertContext == null)
{
    _pConvertContext = CreateContext(sourcePixFmt, targePixFmt);
}

if (_convertedFrameBufferPtr == IntPtr.Zero)
{
    int buffSize = ffmpeg.av_image_get_buffer_size(targePixFmt, sourceFrame->width, sourceFrame->height, 1);
    _convertedFrameBufferPtr = Marshal.AllocHGlobal(buffSize);
     ffmpeg.av_image_fill_arrays(ref _dstData, ref _dstLinesize, (byte*)_convertedFrameBufferPtr, targePixFmt, sourceFrame->width, sourceFrame->height, 1);
}

return ScaleImage(_pConvertContext, sourceFrame, targePixFmt, _dstData, _dstLinesize);

And ScaleImage method

ffmpeg.sws_scale(ctx, sourceFrame->data, sourceFrame->linesize, 0, sourceFrame->height, dstData, dstLinesize);

AVFrame* f = ffmpeg.av_frame_alloc();

var data = new byte_ptrArray8();
data.UpdateFrom(dstData);
var linesize = new int_array8();
linesize.UpdateFrom(dstLinesize);

f->data = data;
f->linesize = linesize;
f->width = sourceFrame->width;
f->height = sourceFrame->height;
f->format = (int)targePixelFormat;

return f;

After that sending the scaled frame to the encoder and receiving it and writing the file. After that I call av_frame_free(&frame) on the frame returned from the method. But when I set breakpoint I can see the address of the frame is the same even after calling av_frame_alloc() and cleaning everytime. And I think this is the reason for the memory leak. If I do deep clone of the f before returning it everything is fine. Why is that happening while the same logic works fine with the other camera?

Perhaps you should use `av_frame_unref` instead of `av_frame_free`. — the kamilz, Mar 02 '20 at 07:08

score 2 · Answer 1 · answered Mar 05 '20 at 15:17

Well, after 3 lost days of trying to figure out why it happens with certain cameras only, I've made a memory dump using DebugDiag 2 with a memory leak tracker. It turned out there is tons of memory allocations by _aligned_offset_malloc as you can see in the picture below. I was using ffmpeg 4.2.2, downgrading to 4.0.2 fixed the problem for me. No memory leak now. I'm using 32bit version.

Ffmpeg possible sws_scale memory leak

1 Answers1