[x264-devel] possible bug with b_intra_refresh

[Jason Garrett-Glaser]

On Sun, Apr 11, 2010 at 7:59 PM, Kelvin Chua <kelchy at gmail.com> wrote:
> i am currently doing a video telephony application via ffmpeg and
> encountered a SIGSEGV whenever i increase my resolution
> from QCIF to CIF or VGA.

What?  x264 doesn't support switching resolutions in mid-flight.

> here is a backtrace:
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0xb0d77b70 (LWP 6549)]
> 0x01080b52 in x264_me_search_ref () from /usr/local/lib/libx264.so.83
> (gdb) bt
> #0  0x01080b52 in x264_me_search_ref () from /usr/local/lib/libx264.so.83
> #1  0x01077f60 in ?? () from /usr/local/lib/libx264.so.83
> #2  0x0107b049 in x264_macroblock_analyse () from
> /usr/local/lib/libx264.so.83
> #3  0x010a34f2 in ?? () from /usr/local/lib/libx264.so.83
> #4  0x010bf94b in ?? () from /usr/local/lib/libx264.so.83
> #5  0x0109d5fb in ?? () from /usr/local/lib/libx264.so.83
> #6  0x010a1441 in x264_encoder_encode () from /usr/local/lib/libx264.so.83
> #7  0x00539b47 in ?? () from /usr/local/lib/libavcodec.so.52
> #8  0x0806de81 in H264Encoder::EncodeFrame (this=0x8614498,
>     in=0xb0495008
> "SSSTTTVVVWXXYYZZ[\\\\\\]]^^^__aaccdeeeefffggggfeefghijjjjkklll", 'm'
> <repeats 19 times>, "llkkkkllmmmmmmmm", 'l' <repeats 20 times>,
> "kkjjjjjjkklll", 'm' <repeats 13 times>,
> "nnoopooooooooonnmlkkkkkkkkkjjjjjjjj", 'k' <repeats 14 times>,
> "jjjjjjjkkkl"..., len=460800)
> *H264Encoder::EncodeFrame is a function in my app
> here is my encoding parameters:
>         ctx->rc_max_rate        = (int) (((float)bitrate)*0.9/1000.0);
>         ctx->rc_min_rate        = ctx->rc_max_rate;
>         ctx->rc_buffer_size     = ctx->rc_max_rate;
>         ctx->intra_refresh      = 1;    //params.b_intra_refresh
>         ctx->sliced_threads     = 1;    //params.b_sliced_threads
>         ctx->me_range           = 16;    //analyse.i_me_range
>         ctx->qmin               = 10;   //rc.i_qp_min
>         ctx->qcompress          = 0.6;    //rc.f_qcompress
>         ctx->max_qdiff          = 12;    //rc.i_qp_step
>         ctx->b_quant_factor     = 1.3; //minimum 1.26 params.rc.f_pb_factor
>         ctx->i_quant_factor     = 1.4; //minimum 0.78
> 1/params.rc.f_ip_factor
>         ctx->max_b_frames       = 0;    //params.i_bframe
>         ctx->keyint_min         = 10;   //min-keyint
>         ctx->coder_type         = 0;    //params.b_cabac
>         ctx->gop_size           = 60;   //keyint or keyint_max
>         ctx->b_annexb           = 0;    //disable start code prefix
>         ctx->level              = 30;
>         ctx->rtp_payload_size   = MTU-100; //params.i_slice_max_size
>         ctx->weighted_p_pred    = 0;    //params.analyse.i_weighted_pred
>         ctx->directpred         = 1;    //params.analyse.i_direct_mv_pred
>         ctx->flags |= CODEC_FLAG_PASS1;                 //PASS1
>         ctx->flags &= ~CODEC_FLAG_4MV;                  //advanced
> prediction
> whenever i disable b_intra_refresh, everything works perfectly. however i
> wanted to enable
> intra_refresh as i see a huge performance boost with it on QCIF resolution.
> especially on a lossy network.
> Kelvin Chua

Have you tried using libx264 directly instead of through libavcodec?
We don't generally support using libx264 through libavcodec as it has
a history of causing all kinds of problems (and it's also a big
hassle).

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