webrtc - 强制左/右立体声

Question

我正在尝试生成具有 L/R 立体声的低比特率作品文件。是什么决定 opusenc 是否使用 L/R 立体声而不是联合立体声？有我可以通过的标志吗？与比特率有关吗？

opusenc input.wav output.opus //produces L/R stereo
opusenc input.wav output.opus --bitrate 8 //produces joint stereo

Answer 1

看来已经确定了here :

    if (st->force_channels!=OPUS_AUTO && st->channels == 2)
    {
        st->stream_channels = st->force_channels;
    } else {
#ifdef FUZZING
       /* Random mono/stereo decision */
       if (st->channels == 2 && (rand()&0x1F)==0)
          st->stream_channels = 3-st->stream_channels;
#else
       /* Rate-dependent mono-stereo decision */
       if (st->channels == 2)
       {
          opus_int32 stereo_threshold;
          stereo_threshold = stereo_music_threshold + ((voice_est*voice_est*(stereo_voice_threshold-stereo_music_threshold))>>14);
          if (st->stream_channels == 2)
             stereo_threshold -= 4000;
          else
             stereo_threshold += 4000;
          st->stream_channels = (equiv_rate > stereo_threshold) ? 2 : 1;
       } else {
          st->stream_channels = st->channels;
       }
#endif
    }

只要简单地阅读一下 opusenc 源代码，看起来在 struct OpusEncoder 上将 force_channels 设置为 2 就可以让它工作了。然而，查看opusenc.c源代码，没有发现该字段在哪里设置。您可以轻松修改源，但始终强制 channel 为两个。对于 future ，opus 似乎称其为“双立体声”而不是“L/R 立体声”。