Alex Rivera | Logout

How to encode h.264 with libavcodec/x264?

Asked 2010-08-24T01:45:25.703
23

I am attempting to encode video using libavcodec/libavformat. Audio works great, but when I try to encode video I get the following errors:

[libx264 @ 0x10182a000]broken ffmpeg default settings detected  
[libx264 @ 0x10182a000]use an encoding preset (vpre)

easy to fix using the command line ffmpeg, but I am trying to do this in C. my options are

AVStream *pVideoOutStream = av_new_stream(pOutFormatCtx, 0);  
AVCodecContext *pVideoOutCodecCtx  = pVideoOutStream->codec;  

pVideoOutCodecCtx->codec_id        = CODEC_ID_H264;    
pVideoOutCodecCtx->codec_type      = CODEC_TYPE_VIDEO;  
pVideoOutCodecCtx->bit_rate        = pVideoInCodecCtx->bit_rate;  
pVideoOutCodecCtx->width           = pVideoInCodecCtx->width;    
pVideoOutCodecCtx->height          = pVideoInCodecCtx->height;  
pVideoOutCodecCtx->pix_fmt         = pVideoInCodecCtx->pix_fmt;    
pVideoOutCodecCtx->sample_rate     = pVideoInCodecCtx->sample_rate;    
pVideoOutCodecCtx->gop_size        = 30;

but avcodec_open() fails.

What other values do I need to set to make x264 happy?

c x264 libavcodec libx264 libav
Edit
Report

1 Answer

12

Not sure whether you got it working, but the following parameters work for me.

ctx->bit_rate = 500*1000;
ctx->bit_rate_tolerance = 0;
ctx->rc_max_rate = 0;
ctx->rc_buffer_size = 0;
ctx->gop_size = 40;
ctx->max_b_frames = 3;
ctx->b_frame_strategy = 1;
ctx->coder_type = 1;
ctx->me_cmp = 1;
ctx->me_range = 16;
ctx->qmin = 10;
ctx->qmax = 51;
ctx->scenechange_threshold = 40;
ctx->flags |= CODEC_FLAG_LOOP_FILTER;
ctx->me_method = ME_HEX;
ctx->me_subpel_quality = 5;
ctx->i_quant_factor = 0.71;
ctx->qcompress = 0.6;
ctx->max_qdiff = 4;
ctx->directpred = 1;
ctx->flags2 |= CODEC_FLAG2_FASTPSKIP;

The error message broken ffmpeg default settings detected is displayed in the x264 library in x264/encoder/encoder.c when too many settings are the default ffmpeg settings (e.g. qmin = 2, qmax = 31, qcompress = 0.5), changing these three values to something else, e.g. qmin = 10, qmax = 51, qcompress = 0.6, resolves the error.

answered 2010-08-30T15:13:37.480

Your Answer