audio - 寻找一种通用方法来合并音频和视频文件并使用 FFmpeg 使输出具有立体声音频

Question

所以有以下 FFmpeg 命令

ffmpeg -i vidab.mp4 -i recab.webm  -filter_complex "[0:a]volume=0.2,apad[A];[1:a][A]amerge[Aout]" -map 0:v -map [Aout] -y mergeab.mp4

当输入文件单独播放时，它们的音频通过两个耳机平等地播放。

但是在合并后，视频中的音频在右侧，而 webm 文件中的音频在左侧。

当我运行 cmd 时，我在输出中看到了这一点

[Parsed_amerge_2 @ 0x7fa0faf01bc0] No channel layout for input 1
[Parsed_amerge_2 @ 0x7fa0faf01bc0] Input channel layouts overlap: output layout will be determined by the number of distinct input channels

我该如何调整它，以使输出文件的左右两侧输入的音频均等？

还有一种通用的方法可以做到这一点，即使是不同的配置(视频有立体声，音频有单声道......或两者都有立体声)也会导致音频被平均分割。

我尝试使用平移过滤器，但我不明白它是如何工作的，因为要么什么也没发生，要么我左右翻转。但我什至没有立体感。

fwiw 这里是完整的输出。

ffmpeg -i vidab.mp4 -i recab.webm  -filter_complex "[0:a]volume=0.2,apad[A];[1:a][A]amerge[Aout]" -map 0:v -map [Aout] -y mergeab.mp4
ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple clang version 11.0.0 (clang-1100.0.33.8)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.1_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home/include/darwin -fno-stack-check' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vidab.mp4':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    creation_time   : 2020-02-21T00:35:25.000000Z
  Duration: 00:00:10.65, start: 0.000000, bitrate: 2539 kb/s
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 96 kb/s (default)
    Metadata:
      creation_time   : 2020-02-21T00:35:25.000000Z
      handler_name    : Core Media Audio
    Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1280x640, 2436 kb/s, 29.87 fps, 29.97 tbr, 90k tbn, 180k tbc (default)
    Metadata:
      creation_time   : 2020-02-21T00:35:25.000000Z
      handler_name    : Core Media Video
      encoder         : H.264
Input #1, matroska,webm, from 'recab.webm':
  Metadata:
    encoder         : opus-media-recorder
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #1:0(eng): Audio: opus, 48000 Hz, mono, fltp (default)
Stream mapping:
  Stream #0:0 (aac) -> volume (graph 0)
  Stream #1:0 (opus) -> amerge:in0 (graph 0)
  Stream #0:1 -> #0:0 (h264 (native) -> h264 (libx264))
  amerge (graph 0) -> Stream #0:1 (aac)
Press [q] to stop, [?] for help
[libx264 @ 0x7fa0fb004000] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7fa0fb004000] profile High, level 3.1
[libx264 @ 0x7fa0fb004000] 264 - core 155 r2917 0a84d98 - 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=12 lookahead_threads=2 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
[Parsed_amerge_2 @ 0x7fa0faf01bc0] No channel layout for input 1
[Parsed_amerge_2 @ 0x7fa0faf01bc0] Input channel layouts overlap: output layout will be determined by the number of distinct input channels
Output #0, mp4, to 'mergeab.mp4':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    encoder         : Lavf58.29.100
    Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuvj420p(pc, progressive), 1280x640, q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default)
    Metadata:
      creation_time   : 2020-02-21T00:35:25.000000Z
      handler_name    : Core Media Video
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      encoder         : Lavc58.54.100 aac
frame=  318 fps=107 q=-1.0 Lsize=    1568kB time=00:00:17.72 bitrate= 724.8kbits/s speed=5.99x    
video:1282kB audio:272kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.902630%
[libx264 @ 0x7fa0fb004000] frame I:2     Avg QP:19.72  size: 51154
[libx264 @ 0x7fa0fb004000] frame P:148   Avg QP:21.28  size:  6644
[libx264 @ 0x7fa0fb004000] frame B:168   Avg QP:25.18  size:  1351
[libx264 @ 0x7fa0fb004000] consecutive B-frames:  1.3% 84.9%  0.0% 13.8%
[libx264 @ 0x7fa0fb004000] mb I  I16..4: 23.2% 49.3% 27.5%
[libx264 @ 0x7fa0fb004000] mb P  I16..4:  2.1%  2.0%  0.2%  P16..4: 29.0%  5.1%  4.8%  0.0%  0.0%    skip:56.8%
[libx264 @ 0x7fa0fb004000] mb B  I16..4:  0.5%  0.3%  0.0%  B16..8: 16.7%  0.8%  0.2%  direct: 6.1%  skip:75.4%  L0:24.8% L1:71.1% BI: 4.1%
[libx264 @ 0x7fa0fb004000] 8x8 transform intra:45.4% inter:74.3%
[libx264 @ 0x7fa0fb004000] coded y,uvDC,uvAC intra: 29.3% 51.4% 11.6% inter: 5.7% 16.6% 0.3%
[libx264 @ 0x7fa0fb004000] i16 v,h,dc,p: 11% 53% 10% 26%
[libx264 @ 0x7fa0fb004000] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 13% 36% 35%  2%  2%  2%  4%  2%  3%
[libx264 @ 0x7fa0fb004000] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 24% 30% 12%  4%  6%  5%  7%  5%  6%
[libx264 @ 0x7fa0fb004000] i8c dc,h,v,p: 47% 33% 17%  4%
[libx264 @ 0x7fa0fb004000] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7fa0fb004000] ref P L0: 76.6%  7.6% 11.1%  4.7%
[libx264 @ 0x7fa0fb004000] ref B L0: 89.1% 10.3%  0.6%
[libx264 @ 0x7fa0fb004000] ref B L1: 99.7%  0.3%
[libx264 @ 0x7fa0fb004000] kb/s:989.60
[aac @ 0x7fa0fb005800] Qavg: 13376.354

Answer 1

使用amix而不是 amerge并使用 -ac 2 重新采样为立体声.由于您正在映射第一个视频，因此请告诉 amix 以第一个输入终止。
ffmpeg -i vidab.mp4 -i recab.webm -filter_complex "[0:a]volume=0.2[A];[A][1:a]amix=inputs=2:duration=first[Aout]" -map 0:v -map [Aout] -y mergeab.mp4