[Libav-user] OpenCV VideoCapture FFmpeg Module Bug on Linux using Video without a Codec

[Rafael Lúcio]

I'm not an expert but maybe I can give u a simpler solution.... just ignore
if I'm talking nonsense stuffs..

maybe if u just av_init_packet before av_free_packet your problem is solved
and you don't have memory leak.
I haven't tested this theory, its just an idea.

2015-03-05 8:30 GMT-03:00 Johannes Rehm <hahne.rehm at gmx.de>:

> Hi All,
>
> there is a known bug in the VideoCapture ffmpeg module of OpenCV. It
> occurs while loading videos without  a codec:
> http://code.opencv.org/issues/1915
> I had some time now to debug this bug and found the issue in:
> CvCapture_FFMPEG::grabFrame()
> In the function
> avcodec_decode_video2(video_st->codec, picture, &got_picture, &packet);
> the AVFrame picture get set. But after
> av_free_packet (&packet);
> I get: "error: Cannot access memory at address..." for picture.data[0]
> which leads to a segmentation fault later in the function sws_scale().
> I can encode this video with a video codec using ffmpeg or whatever and I
> get no segmentation fault (memory in picture.data[0] can still be accessed).
> Of course there is an easy fix for this bug: Simply comment out / delete
> av_free_packet (&packet);
> This is working fine for me. Now I can process videos with and without
> codecs. But I am not sure if this will lead to memory issues if
> av_free_packet gets not called. Is there anybody who is familiar with the
> FFmpeg interface of OpenCV and can help me here?
> Thanks a lot!
>
> Best regards,
> Johannes Rehm
>
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>
>


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Rafael Lúcio
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