JavaCV推流写音频帧报错：org.bytedeco.javacv.FrameRecorder$Exception: avcodec_encode_audio2() error -12: Could not encode audio packet.

　　我们在设置推流的音频配置时（详细代码参见JavaCV本地视频流通过帧图片添加文本进行字幕合成），指定原拉流时的音频编码器：

        // 音频相关配置，取原音频配置
        recorder.setSampleRate(grabber.getSampleRate());
        System.out.println(grabber.getAudioCodec());
        recorder.setAudioCodec(grabber.getAudioCodec());

　　我们看输出：

86021
准备开始推流...
Exception in thread "main" org.bytedeco.javacv.FrameRecorder$Exception: avcodec_encode_audio2() error -12: Could not encode audio packet.
    at org.bytedeco.javacv.FFmpegFrameRecorder.record(FFmpegFrameRecorder.java:1203)
    at org.bytedeco.javacv.FFmpegFrameRecorder.writeSamples(FFmpegFrameRecorder.java:1193)
    at org.bytedeco.javacv.FFmpegFrameRecorder.recordSamples(FFmpegFrameRecorder.java:1167)
    at org.bytedeco.javacv.FFmpegFrameRecorder.record(FFmpegFrameRecorder.java:922)
    at org.bytedeco.javacv.FFmpegFrameRecorder.record(FFmpegFrameRecorder.java:911)
    at com.lxy.service.SubtitleMix.main(SubtitleMix.java:78)
Input #0, matroska,webm, from 'E:BaiduNetdiskDownload	estout.mkv':
  Metadata:
    title           : 天下足球网 http://www.txzqw.cc
    ENCODER         : Lavf58.39.101
  Duration: 00:01:11.11, start: 0.000000, bitrate: 2485 kb/s
    Stream #0:0: Video: h264 (High), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
    Metadata:
      ENCODER         : Lavc58.73.102 libx264
      DURATION        : 00:01:09.243000000
    Stream #0:1: Audio: vorbis, 48000 Hz, 5.1, fltp (default)
    Metadata:
      ENCODER         : Lavc58.73.102 libvorbis
      DURATION        : 00:01:09.331000000
    Stream #0:2: Subtitle: ass
    Metadata:
      ENCODER         : Lavc58.73.102 ssa
      DURATION        : 00:01:11.113000000
[libx264 @ 000000001cfa9a80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 000000001cfa9a80] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 000000001cfa9a80] 264 - core 157 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'E:BaiduNetdiskDownloadouttest.mp4':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 1280x720, q=2-31, 25 fps, 12800 tbn, 25 tbc
    Stream #0:1: Audio: vorbis (mp4a / 0x6134706D), 48000 Hz, stereo, fltp

　　根据日志找到源码：

if ((ret = avcodec.avcodec_encode_audio2(this.audio_c, this.audio_pkt, frame, this.got_audio_packet)) < 0) {
            throw new Exception("avcodec_encode_audio2() error " + ret + ": Could not encode audio packet.");
        } 

　　再跟：

public static native int avcodec_encode_audio2(AVCodecContext var0, AVPacket var1, @Const AVFrame var2, int[] var3);

　　又是一条死胡同。至少我们知道原来的音视频采用的音频编码器是86021，一搜发现

　　说明这个编码器不行，指定使用MP3编码器（就是上面的86017），问题解决。