[Libav-user] avcodec_encode_video2() crashes after encoding a few pictures

[Paul B Mahol]

On 6/27/13, Arvind Raman <arvind_raman at yahoo.com> wrote:
> I am developing an application using the FFmpeg libraries and am facing a
> crash issue that I am finding extremely hard to debug. My printf logs
> suggest that crash happens within the avcodec_encode_video2() function but I
> am not sure what is causing the crash.
>
> Just for debugging purpose, I created the following infinite loop on the
> "encode" thread. The loop iterates several times and crashes somewhere in
> between the 350th and the 400th iteration. The crash is not deterministic.
> Please note there are video decode (libavcodec) and demux (libavformat)
> threads running in parallel that are interrupting the
> avcodec_encode_video2() function. Could this be a problem.
>
> Do you spot anything that might be causing the crash? I am using the x.264
> encoder. The only error log that I get on the terminal is "Segmentation
> fault (core dumped)" so I am finding it hard to proceed. Is there anyway to
> get x.264 to print where the crash might be happening.
>
> Its quite likely that this might be a silly coding mistake from my end, but
> just wanted to get a quick check done from you all and receive your
> suggestions.
>
> while(1)
> {
>     av_init_packet(&encode_packet);
>     frame->pts += 3750;
>
>     frame->data[0] = frame_buf;
>     frame->data[1] = frame->data[0] + (frame->linesize[0] *
> encoder_ctx->height);
>     frame->data[2] = frame->data[1] + (frame->linesize[1] *
> (encoder_ctx->height / 2));

This looks wrong, use memcpy instead.

>     encode_status = avcodec_encode_video2(encoder_ctx, &encode_packet,
> frame, &got_packet);
>
>     av_free_packet(&encode_packet);
> }
>
> I tried running valgrind as well but that didn't throw any illegal memory
> access and it throws the following error. Could this be causing the crash?
> What is this error about? I saw similar error messages elsewhere as well,
> but don't think I found any solution there.
>
>
> vex amd64->IR: unhandled instruction bytes: 0x66 0xF 0x38 0x41 0xC0 0x66 0xF
> 0x7E
> ==10933== valgrind: Unrecognised instruction at address 0x51393bc.
> ==10933==    at 0x51393BC: ??? (in /usr/local/lib/libx264.so.133)
> ==10933==    by 0x2000200020001F: ???
> ==10933== Your program just tried to execute an instruction that Valgrind
> ==10933== did not recognise.  There are two possible reasons for this.
> ==10933== 1. Your program has a bug and erroneously jumped to a non-code
> ==10933==    location.  If you are running Memcheck and you just saw a
> ==10933==    warning about a bad jump, it's probably your program's fault.
> ==10933== 2. The instruction is legitimate but Valgrind doesn't handle it,
> ==10933==    i.e. it's Valgrind's fault.  If you think this is the case or
> ==10933==    you are not sure, please let us know and we'll try to fix it.
> ==10933== Either way, Valgrind will now raise a SIGILL signal which will
> ==10933== probably kill your program.
> ==10933==
> ==10933== Process terminating with default action of signal 4 (SIGILL)
> ==10933==  Illegal opcode at address 0x51393BC
> ==10933==    at 0x51393BC: ??? (in /usr/local/lib/libx264.so.133)
> ==10933==    by 0x2000200020001F: ???
>
> Any help would be greatly appreciated!!!
>
> Best regards
> Arvind
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