C语言 如何使用 libavcodec/x264 编码 h.264？

How to encode h.264 with libavcodec/x264?

提问by szatmary

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

我正在尝试使用 libavcodec/libavformat 对视频进行编码。音频效果很好，但是当我尝试对视频进行编码时，出现以下错误：

[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

使用命令行 ffmpeg 很容易修复，但我试图在 C 中做到这一点。我的选择是

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.

但 avcodec_open() 失败。

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

我需要设置哪些其他值才能使 x264 满意？

采纳答案by Shea

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

不确定你是否让它工作，但以下参数对我有用。

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;

---

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The error message broken ffmpeg default settings detectedis displayed in the x264 library in x264/encoder/encoder.cwhen 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.

当太多设置是默认 ffmpeg 设置（例如）时，错误消息broken ffmpeg default settings detected会显示在x264/encoder/encoder.c中的 x264 库中qmin = 2, qmax = 31, qcompress = 0.5，将这三个值更改为其他值，例如qmin = 10, qmax = 51, qcompress = 0.6，可以解决错误。

回答by Sergey Skopus

Don't forget to use x264 private options. You can always set a profile:

不要忘记使用 x264 私有选项。您始终可以设置配置文件：

av_dict_set(&This->opts, "vprofile", "baseline", 0)

Or set the lowest encoding latency:

或者设置最低的编码延迟：

av_dict_set(&This->opts, "tune", "zerolatency", 0);

Or select a preset:

或者选择一个预设：

av_dict_set(&This->opts, "preset","ultrafast",0);

Before opening a codec

在打开编解码器之前

avcodec_open2(This->context, This->codec, &This->opts)

回答by Pada

The following is how to interpret the ffmpeg's x264 presets.

下面是如何解读ffmpeg的x264预设。

Unfortunately I don't know of an easy way to import the presets like ffmpeg does. You can lookup the x264 preset values which are all stored in /usr/local/share/ffmpeg/libx264-{name}.ffpreset, where {name} is specified for ffmpeg as the -vpre {name} command-line argument. So typically ffmpeg would include libx264-medium.ffpreset and then libx264-main.ffpreset, specified as ffmpeg -vpre medium -vpre main

不幸的是，我不知道像 ffmpeg 那样导入预设的简单方法。您可以查找所有存储在 /usr/local/share/ffmpeg/libx264-{name}.ffpreset 中的 x264 预设值，其中为 ffmpeg 指定 {name} 作为 -vpre {name} 命令行参数。所以通常 ffmpeg 会包含 libx264-medium.ffpreset 和 libx264-main.ffpreset，指定为 ffmpeg -vpre medium -vpre main

You can lookup all the options (as defined in the libx264-{name}.ffpreset files) to get their structure names by looking in the libavcodec/options.c file, which can be found in the ffmpeg SVN repositories.

您可以通过查看 libavcodec/options.c 文件（可在 ffmpeg SVN 存储库中找到）来查找所有选项（如 libx264-{name}.ffpreset 文件中所定义）以获取其结构名称。

Here's how the medium and main presets would be translated into C code:

以下是将媒体和主要预设转换为 C 代码的方式：

// libx264-medium.ffpreset preset
ctx->coder_type = 1;  // coder = 1
ctx->flags|=CODEC_FLAG_LOOP_FILTER;   // flags=+loop
ctx->me_cmp|= 1;  // cmp=+chroma, where CHROMA = 1
ctx->partitions|=X264_PART_I8X8+X264_PART_I4X4+X264_PART_P8X8+X264_PART_B8X8; // partitions=+parti8x8+parti4x4+partp8x8+partb8x8
ctx->me_method=ME_HEX;    // me_method=hex
ctx->me_subpel_quality = 7;   // subq=7
ctx->me_range = 16;   // me_range=16
ctx->gop_size = 250;  // g=250
ctx->keyint_min = 25; // keyint_min=25
ctx->scenechange_threshold = 40;  // sc_threshold=40
ctx->i_quant_factor = 0.71; // i_qfactor=0.71
ctx->b_frame_strategy = 1;  // b_strategy=1
ctx->qcompress = 0.6; // qcomp=0.6
ctx->qmin = 10;   // qmin=10
ctx->qmax = 51;   // qmax=51
ctx->max_qdiff = 4;   // qdiff=4
ctx->max_b_frames = 3;    // bf=3
ctx->refs = 3;    // refs=3
ctx->directpred = 1;  // directpred=1
ctx->trellis = 1; // trellis=1
ctx->flags2|=CODEC_FLAG2_BPYRAMID+CODEC_FLAG2_MIXED_REFS+CODEC_FLAG2_WPRED+CODEC_FLAG2_8X8DCT+CODEC_FLAG2_FASTPSKIP;  // flags2=+bpyramid+mixed_refs+wpred+dct8x8+fastpskip
ctx->weighted_p_pred = 2; // wpredp=2

// libx264-main.ffpreset preset
ctx->flags2|=CODEC_FLAG2_8X8DCT;c->flags2^=CODEC_FLAG2_8X8DCT;    // flags2=-dct8x8

You'll have to look at the ffmpeg source code if you want to parse those presets automatically.

如果要自动解析这些预设，则必须查看 ffmpeg 源代码。

I hope that the information I just gave would help you out a bit more :)

我希望我刚刚提供的信息对您有所帮助:)

回答by Petroff

I encode YUV420P pictures into different formats, using different codecs. CodecID I took from AVOutputFormat after using guess_format(...) function. But other codec settings are (All of them has been taken from ffmpeg examples' source code):

我使用不同的编解码器将 YUV420P 图片编码为不同的格式。CodecID 我在使用 guess_format(...) 函数后从 AVOutputFormat 中获取。但其他编解码器设置是（所有这些都取自 ffmpeg 示例的源代码）：

c->codec_id = (CodecID)CODEC_ID_H264; //This is your codec id
c->codec_type = CODEC_TYPE_VIDEO;

c->bit_rate = 1000000;  
c->width = <...>;  
c->height = <...>;  
c->time_base.den = 25;  
c->time_base.num = 1;  
c->gop_size = 12;  
c->pix_fmt = PIX_FMT_YUV420P;  
if (c->codec_id == CODEC_ID_MPEG1VIDEO) //It not necessary for you 
   c->mb_decision=2;  
// some formats want stream headers to be separate  
if(oc->oformat->flags & AVFMT_GLOBALHEADER)  
   c->flags |= CODEC_FLAG_GLOBAL_HEADER; 

This setting must work to most codecs, but I had a problem with fps: not all codecs supports any fps values (and some other parameters too).

此设置必须适用于大多数编解码器，但我遇到了 fps 问题：并非所有编解码器都支持任何 fps 值（以及其他一些参数）。

回答by Jochen

seems that the ffmpeg version 20130302 requires something like

似乎 ffmpeg 版本 20130302 需要类似的东西

c->profile = FF_PROFILE_H264_BASELINE;