我正在尝试拍摄具有h264视频轨道和dts-ma音轨的视频，然后输出.m4v文件：
h264视频曲目 DTS-ma音轨 AC-3 5.1音轨
我正在尝试复制视频和dts-ma音轨，然后将其转换为AC-3音轨
我从此命令收到错误Unable to find a suitable output format for 'ac3'：
ffmpeg -i "input.mkv" -map 0:0 -map 0:1 -map 0:1 -map 0:1 -c:v copy -c:a:0 copy -c:a:1 -acodec ac3 -ac 6 -ab 448k -c:a:2 -acodec ac3 -ac 6 -ab 256 -ar 48000 "output.m4v"
（这是由我的C＃app生成的）
这对于已经安装了h264和ac3的其他文件可以正常工作：
ffmpeg -i "input.mkv" -map 0:0 -map 0:1 -c:v copy -c:a:0 copy "output.m4v"
显然它没有做转换。
以下是第一个命令的完整结果：
ffmpeg version N-46936-g8b6aeb1 Copyright (c) 2000-2012 the FFmpeg developers
built on Nov 20 2012 19:34:37 with gcc 4.7.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-pthreads --enable-runtime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libass -
-enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-libnut --enable-libopenjpeg --enable-libo
pus --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libutvideo --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-li
bvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
libavutil 52. 8.100 / 52. 8.100
libavcodec 54. 74.100 / 54. 74.100
libavformat 54. 37.100 / 54. 37.100
libavdevice 54. 3.100 / 54. 3.100
libavfilter 3. 23.101 / 3. 23.101
libswscale 2. 1.102 / 2. 1.102
libswresample 0. 17.101 / 0. 17.101
libpostproc 52. 2.100 / 52. 2.100
Input #0, matroska,webm, from 'input.mkv':
Metadata:
creation_time : 2012-12-07 22:11:56
Duration: 01:41:23.38, start: 0.000000, bitrate: 33582 kb/s
Chapter #0.0: start 0.000000, end 186.250000
Metadata:
title : 00:00:00.000
Chapter #0.1: start 186.250000, end 512.708000
Metadata:
title : 00:03:06.250
Chapter #0.2: start 512.708000, end 883.292000
Metadata:
title : 00:08:32.708
Chapter #0.3: start 883.292000, end 1354.000000
Metadata:
title : 00:14:43.292
Chapter #0.4: start 1354.000000, end 1865.458000
Metadata:
title : 00:22:34.000
Chapter #0.5: start 1865.458000, end 2122.500000
Metadata:
title : 00:31:05.458
Chapter #0.6: start 2122.500000, end 2386.125000
Metadata:
title : 00:35:22.500
Chapter #0.7: start 2386.125000, end 2801.167000
Metadata:
title : 00:39:46.125
Chapter #0.8: start 2801.167000, end 2923.000000
Metadata:
title : 00:46:41.167
Chapter #0.9: start 2923.000000, end 3388.500000
Metadata:
title : 00:48:43.000
Chapter #0.10: start 3388.500000, end 3808.167000
Metadata:
title : 00:56:28.500
Chapter #0.11: start 3808.167000, end 4071.375000
Metadata:
title : 01:03:28.167
Chapter #0.12: start 4071.375000, end 4378.750000
Metadata:
title : 01:07:51.375
Chapter #0.13: start 4378.750000, end 4681.583000
Metadata:
title : 01:12:58.750
Chapter #0.14: start 4681.583000, end 4989.792000
Metadata:
title : 01:18:01.583
Chapter #0.15: start 4989.792000, end 5311.667000
Metadata:
title : 01:23:09.792
Chapter #0.16: start 5311.667000, end 5629.083000
Metadata:
title : 01:28:31.667
Chapter #0.17: start 5629.083000, end 6083.382000
Metadata:
title : 01:33:49.083
Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 24 fps, 24 tbr, 1k tbn, 48 tbc (default)
Stream #0:1(eng): Audio: dts (DTS-HD MA), 48000 Hz, 5.1(side), fltp, 1536 kb/s (default)
[NULL @ 03f4b020] Unable to find a suitable output format for 'ac3'
ac3: Invalid argument
答案 0 :(得分：7)
问题可能是因为添加了参数-acodec。
-acodec是-codec:a或-c:a的别名。
由于您已使用-c:a:X指定了曲目，因此您不需要-acodec。
这应该有效：
ffmpeg -i "input.mkv" -map 0:0 -map 0:1 -map 0:1 -map 0:1 -c:v copy -c:a:0 copy -c:a:1 ac3 -ac 6 -ab 448k -c:a:2 ac3 -ac 6 -ab 256 -ar 48000 "output.m4v"