ffmpeg 音频转换：编码器 pcm_u8 工作 pcm_s8 不

Question

我需要将视频中的音频转换为 8 位签名的 PCM。我是这样尝试的：

C:\Users\E\Desktop\ffmpeg-20160731-04da20e-win32-static\bin>ffmpeg -i minions.mp4 -vcodec mjpeg -s 800x480 -acodec pcm_s8 -ac 1 out.avi

输出：

ffmpeg version N-81192-g04da20e Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-lib
ebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfree
type --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-lib
openjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame
 --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-
libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 28.100 / 55. 28.100
  libavcodec     57. 51.100 / 57. 51.100
  libavformat    57. 44.100 / 57. 44.100
  libavdevice    57.  0.102 / 57.  0.102
  libavfilter     6. 49.100 /  6. 49.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'minions.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2016-03-17 10:06:57
  Duration: 00:03:18.72, start: 0.000000, bitrate: 1869 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1675 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default
)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      creation_time   : 2016-03-17 10:06:58
      handler_name    : IsoMedia File Produced by Google, 5-11-2011
[swscaler @ 04821880] deprecated pixel format used, make sure you did set range correctly
[avi @ 048c0460] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, avi, to 'out.avi':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    encoder         : Lavf57.44.100
    Stream #0:0(und): Video: mjpeg (MJPG / 0x47504A4D), yuvj420p(pc), 800x480 [SAR 16:15 DAR 16:9], q=2-31, 200 kb/s, 23.98 fps, 23.98 tbn, 23.98 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc57.51.100 mjpeg
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: pcm_s8, 44100 Hz, mono, u8, 352 kb/s (default)
    Metadata:
      creation_time   : 2016-03-17 10:06:58
      handler_name    : IsoMedia File Produced by Google, 5-11-2011
      encoder         : Lavc57.51.100 pcm_s8
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
  Stream #0:1 -> #0:1 (aac (native) -> pcm_s8 (native))
Could not write header for output file #0 (incorrect codec parameters ?): Operation not permitted

ffmpeg 无法为输出文件写入头文件。我想提一下，如果将音频编码器选择为 pcm_u8 一切正常。

C:\Users\E\Desktop\ffmpeg-20160731-04da20e-win32-static\bin>ffmpeg -i minions.mp4 -vcodec mjpeg -s 800x480 -acodec pcm_u8 -ac 1 out.avi

输出：

ffmpeg version N-81192-g04da20e Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-lib
ebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfree
type --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-lib
openjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame
 --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-
libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 28.100 / 55. 28.100
  libavcodec     57. 51.100 / 57. 51.100
  libavformat    57. 44.100 / 57. 44.100
  libavdevice    57.  0.102 / 57.  0.102
  libavfilter     6. 49.100 /  6. 49.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  1.100 /  2.  1.100
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'minions.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2016-03-17 10:06:57
  Duration: 00:03:18.72, start: 0.000000, bitrate: 1869 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1675 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default
)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      creation_time   : 2016-03-17 10:06:58
      handler_name    : IsoMedia File Produced by Google, 5-11-2011
File 'out.avi' already exists. Overwrite ? [y/N] y
[swscaler @ 030a1880] deprecated pixel format used, make sure you did set range correctly
[avi @ 04a10460] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times
Output #0, avi, to 'out.avi':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    ISFT            : Lavf57.44.100
    Stream #0:0(und): Video: mjpeg (MJPG / 0x47504A4D), yuvj420p(pc), 800x480 [SAR 16:15 DAR 16:9], q=2-31, 200 kb/s, 23.98 fps, 23.98 tbn, 23.98 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc57.51.100 mjpeg
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: pcm_u8 ([1][0][0][0] / 0x0001), 44100 Hz, mono, u8, 352 kb/s (default)
    Metadata:
      creation_time   : 2016-03-17 10:06:58
      handler_name    : IsoMedia File Produced by Google, 5-11-2011
      encoder         : Lavc57.51.100 pcm_u8
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
  Stream #0:1 -> #0:1 (aac (native) -> pcm_u8 (native))
Press [q] to stop, [?] for help
frame= 4764 fps=250 q=24.8 Lsize=   74247kB time=00:03:18.71 bitrate=3060.8kbits/s speed=10.4x
video:65364kB audio:8558kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.438745%

有什么问题？为什么转换对签名 pcm 不起作用？

无符号和有符号 pcm 的编码器均可用：

C:\Users\E\Desktop\ffmpeg-20160731-04da20e-win32-static\bin>ffmpeg -encoders

 .
 .
 A..... pcm_f32be            PCM 32-bit floating point big-endian
 A..... pcm_f32le            PCM 32-bit floating point little-endian
 A..... pcm_f64be            PCM 64-bit floating point big-endian
 A..... pcm_f64le            PCM 64-bit floating point little-endian
 A..... pcm_mulaw            PCM mu-law / G.711 mu-law
 A..... pcm_s16be            PCM signed 16-bit big-endian
 A..... pcm_s16be_planar     PCM signed 16-bit big-endian planar
 A..... pcm_s16le            PCM signed 16-bit little-endian
 A..... pcm_s16le_planar     PCM signed 16-bit little-endian planar
 A..... pcm_s24be            PCM signed 24-bit big-endian
 A..... pcm_s24daud          PCM D-Cinema audio signed 24-bit
 A..... pcm_s24le            PCM signed 24-bit little-endian
 A..... pcm_s24le_planar     PCM signed 24-bit little-endian planar
 A..... pcm_s32be            PCM signed 32-bit big-endian
 A..... pcm_s32le            PCM signed 32-bit little-endian
 A..... pcm_s32le_planar     PCM signed 32-bit little-endian planar
 A..... pcm_s8               PCM signed 8-bit
 A..... pcm_s8_planar        PCM signed 8-bit planar
 A..... pcm_u16be            PCM unsigned 16-bit big-endian
 A..... pcm_u16le            PCM unsigned 16-bit little-endian
 A..... pcm_u24be            PCM unsigned 24-bit big-endian
 A..... pcm_u24le            PCM unsigned 24-bit little-endian
 A..... pcm_u32be            PCM unsigned 32-bit big-endian
 A..... pcm_u32le            PCM unsigned 32-bit little-endian
 A..... pcm_u8               PCM unsigned 8-bit
 .
 .

Answer 1

我的公司正在使用 FT810 构建设备，这是我想出的转换脚本：

AUDIO_SAMPLE_RATE=8000
VIDEO_FRAME_RATE=8

VIDEO_Y_POS=266 # Place video in 2/3rds up from bottom of screen

ffmpeg -i source/audio.mp3 -r 65535/2733 -vn -c:a libmp3lame -ar $AUDIO_SAMPLE_RATE -ac 1 -ab 128k -y /tmp/resampled.mp3

ffmpeg -i source/video.gif \
       -i /tmp/resampled.mp3  \
       -filter:v scale=420:-2,pad=420:270+ih/2:0:270-ih/2:black \
       -pix_fmt yuvj420p -vcodec mjpeg -acodec pcm_s16le -r:v $VIDEO_FRAME_RATE -b:v 0.1M -ac 1 -shortest -y output/startup.avi

请注意，我正在使用 pcm_s16le，因为文档中说“16 位 PCM 通过在每个位中删除不太重要的 8 位得到部分支持 音频样本。”

Answer 2

AVI 多路复用器调用的 RIFF 函数不支持为 PCM_S8 流写入标签，因此显然这就是您不能将其写入 AVI 或 WAV 的原因。

您可以使用 MOV 或 NUT 格式。

如果您需要使用 AVI，您可以使用 LPCM 的 S16LE、S24LE、S32LE、F32LE、F64LE 和 U8 变体。

---

要使用 IMA ADPCM 进行编码，请使用

ffmpeg -i minions.mp4 -c:v mjpeg -s 800x480 -c:a adpcm_ima_wav -ac 1 out.avi

要使用 mu-law PCM 进行编码，请使用

ffmpeg -i minions.mp4 -c:v mjpeg -s 800x480 -c:a pcm_mulaw -ac 1 out.avi

Answer 3

您的错误不是关于音频，而是关于视频：

[swscaler @ 04821880] deprecated pixel format used, make sure you did set range correctly
[avi @ 048c0460] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
    Last message repeated 1 times

我认为您可以尝试按照要求设置像素格式。它可以解决它。

我想提一下，如果音频编码器选择为 pcm_u8 一切正常。

请通过编辑将用于此转换的命令和输出（包括它在内的“流映射”之前的所有内容）放入您的 qustion。