如果我更改扬声器配置，ffmpeg avcodec_open2将返回-22
我最近一直有一个奇怪的问题。 根据我在Windows（立体声/四/ 5.1）中设置音频配置的方式，对avcodec_open2（）的ffmpeg调用失败，错误-22或只是工作。 我无法找到很多关于这个错误，我想我应该在这里问一下。 主要流程如下：
c = st->codec; avformat_alloc_output_context2(&oc, NULL, NULL, "video.mpeg"); oc->fmt->audio_codec = AV_CODEC_ID_MP2; AVDictionary* dict = NULL; ret = av_dict_set(&dict, "ac", "2", 0); c->request_channels = 2; ret = avcodec_open2(c, codec, &dict); //HERE IT FAILS WITH -22 if speaker configuration is not stereo 编解码器上下文’c’在流中设置如下：
st = avformat_new_stream(oc, *codec); c = st->codec; c->channels = 2; c->channel_layout = AV_CH_LAYOUT_STEREO; c->sample_fmt = AV_SAMPLE_FMT_S16; c->codec_id = codec_id;
其中大部分都是从文档中的复制示例中复制而来的。 如果在Windows中我将输出设置为立体声，一切都按预期工作。
如果我将扬声器配置设置为5.1（6个通道），avcodec_open2将失败并显示错误-22。
所以我很难理解我做错了什么。 通常它不应该是我的扬声器配置和avcodec_open2的结果之间的任何关系。
我需要设置一些其他参数吗？
这是文件libavcodec\avcodec.h的标题取自如何找出这个ffmpeg错误代码的含义？
#if EINVAL > 0 #define AVERROR(e) (-(e)) /**< Returns a negative error code from a POSIX error code, to return from library functions. */ #define AVUNERROR(e) (-(e)) /**< Returns a POSIX error code from a library function error return value. */ #else /* Some platforms have E* and errno already negated. */ #define AVERROR(e) (e) #define AVUNERROR(e) (e) #endif #define AVERROR_UNKNOWN AVERROR(EINVAL) /**< unknown error */ #define AVERROR_IO AVERROR(EIO) /**< I/O error */ #define AVERROR_NUMEXPECTED AVERROR(EDOM) /**< Number syntax expected in filename. */ #define AVERROR_INVALIDDATA AVERROR(EINVAL) /**< invalid data found */ #define AVERROR_NOMEM AVERROR(ENOMEM) /**< not enough memory */ #define AVERROR_NOFMT AVERROR(EILSEQ) /**< unknown format */ #define AVERROR_NOTSUPP AVERROR(ENOSYS) /**< Operation not supported. */ #define AVERROR_NOENT AVERROR(ENOENT) /**< No such file or directory. */ #define AVERROR_EOF AVERROR(EPIPE) /**< End of file. */ #define AVERROR_PATCHWELCOME -MKTAG('P','A','W','E') /**< Not yet implemented in FFmpeg. Patches welcome. */
然后是EINVAL errno.h头文件
#define EINVAL 22 /* Invalid argument */
PS AVERROR表示(-(-22)) = 22
LAYOUT为通道标头channel_layout.h头文件
/** * @file * audio conversion routines */ /* Audio channel masks */ #define AV_CH_FRONT_LEFT 0x00000001 #define AV_CH_FRONT_RIGHT 0x00000002 #define AV_CH_FRONT_CENTER 0x00000004 #define AV_CH_LOW_FREQUENCY 0x00000008 #define AV_CH_BACK_LEFT 0x00000010 #define AV_CH_BACK_RIGHT 0x00000020 #define AV_CH_FRONT_LEFT_OF_CENTER 0x00000040 #define AV_CH_FRONT_RIGHT_OF_CENTER 0x00000080 #define AV_CH_BACK_CENTER 0x00000100 #define AV_CH_SIDE_LEFT 0x00000200 #define AV_CH_SIDE_RIGHT 0x00000400 #define AV_CH_TOP_CENTER 0x00000800 #define AV_CH_TOP_FRONT_LEFT 0x00001000 #define AV_CH_TOP_FRONT_CENTER 0x00002000 #define AV_CH_TOP_FRONT_RIGHT 0x00004000 #define AV_CH_TOP_BACK_LEFT 0x00008000 #define AV_CH_TOP_BACK_CENTER 0x00010000 #define AV_CH_TOP_BACK_RIGHT 0x00020000 #define AV_CH_STEREO_LEFT 0x20000000 ///< Stereo downmix. #define AV_CH_STEREO_RIGHT 0x40000000 ///< See AV_CH_STEREO_LEFT. /** Channel mask value used for AVCodecContext.request_channel_layout to indicate that the user requests the channel order of the decoder output to be the native codec channel order. */ #define AV_CH_LAYOUT_NATIVE 0x8000000000000000LL /* Audio channel convenience macros */ #define AV_CH_LAYOUT_MONO (AV_CH_FRONT_CENTER) #define AV_CH_LAYOUT_STEREO (AV_CH_FRONT_LEFT|AV_CH_FRONT_RIGHT) #define AV_CH_LAYOUT_2_1 (AV_CH_LAYOUT_STEREO|AV_CH_BACK_CENTER) #define AV_CH_LAYOUT_SURROUND (AV_CH_LAYOUT_STEREO|AV_CH_FRONT_CENTER) #define AV_CH_LAYOUT_4POINT0 (AV_CH_LAYOUT_SURROUND|AV_CH_BACK_CENTER) #define AV_CH_LAYOUT_2_2 (AV_CH_LAYOUT_STEREO|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT) #define AV_CH_LAYOUT_QUAD (AV_CH_LAYOUT_STEREO|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT) #define AV_CH_LAYOUT_5POINT0 (AV_CH_LAYOUT_SURROUND|AV_CH_SIDE_LEFT|AV_CH_SIDE_RIGHT) #define AV_CH_LAYOUT_5POINT1 (AV_CH_LAYOUT_5POINT0|AV_CH_LOW_FREQUENCY) #define AV_CH_LAYOUT_5POINT0_BACK (AV_CH_LAYOUT_SURROUND|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT) #define AV_CH_LAYOUT_5POINT1_BACK (AV_CH_LAYOUT_5POINT0_BACK|AV_CH_LOW_FREQUENCY) #define AV_CH_LAYOUT_7POINT0 (AV_CH_LAYOUT_5POINT0|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT) #define AV_CH_LAYOUT_7POINT1 (AV_CH_LAYOUT_5POINT1|AV_CH_BACK_LEFT|AV_CH_BACK_RIGHT) #define AV_CH_LAYOUT_7POINT1_WIDE (AV_CH_LAYOUT_5POINT1_BACK|AV_CH_FRONT_LEFT_OF_CENTER|AV_CH_FRONT_RIGHT_OF_CENTER) #define AV_CH_LAYOUT_STEREO_DOWNMIX (AV_CH_STEREO_LEFT|AV_CH_STEREO_RIGHT)