ffmpeg 转换跳过音频
使用 ffmpeg 将视频转换为 mp4 格式时，音频会被跳过，因为音频与视频不同步。
大家可以看一下下面的视频： https://vialogues.com/vialogues/play/486
我使用以下选项进行转换
/usr/local/bin/ffmpeg -y -i $inputfile -acodec libfaac -ar 44100 -ab 96k -vcodec libx264 -level 41 -bufsize 20000k -maxrate 25000k -g 250 -r 20 -s 480x270 -coder 1 -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -flags2 +dct8x8+bpyramid -me_method umh -subq 7 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -rc_eq 'blurCplx^(1-qComp)' -bf 16 -b_strategy 1 -bidir_refine 1 -refs 6 -crf 25 -deblockalpha 0 -vpre medium -deblockbeta 0 $outputfile
另外 ffmpeg 版本是
ffmpeg
FFmpeg version 0.6.1, Copyright (c) 2000-2010 the FFmpeg developers
built on Feb 19 2011 19:03:56 with gcc 4.4.5
configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
libavutil 50.15. 1 / 50.15. 1
libavcodec 52.72. 2 / 52.72. 2
libavformat 52.64. 2 / 52.64. 2
libavdevice 52. 2. 0 / 52. 2. 0
libswscale 0.11. 0 / 0.11. 0
libpostproc 51. 2. 0 / 51. 2. 0
Hyper fast Audio and Video encoder
关于为什么会发生这种情况的任何想法吗？
While converting a video to mp4 format using ffmpeg the audio gets skipped because of which the audio goes out of sync with the Video.
One can have a look at the following Video:
https://vialogues.com/vialogues/play/486
I am using the following options for conversion
/usr/local/bin/ffmpeg -y -i $inputfile -acodec libfaac -ar 44100 -ab 96k -vcodec libx264 -level 41 -bufsize 20000k -maxrate 25000k -g 250 -r 20 -s 480x270 -coder 1 -flags +loop -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -flags2 +dct8x8+bpyramid -me_method umh -subq 7 -me_range 16 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -rc_eq 'blurCplx^(1-qComp)' -bf 16 -b_strategy 1 -bidir_refine 1 -refs 6 -crf 25 -deblockalpha 0 -vpre medium -deblockbeta 0 $outputfile
Also the ffmpeg version is
ffmpeg
FFmpeg version 0.6.1, Copyright (c) 2000-2010 the FFmpeg developers
built on Feb 19 2011 19:03:56 with gcc 4.4.5
configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
libavutil 50.15. 1 / 50.15. 1
libavcodec 52.72. 2 / 52.72. 2
libavformat 52.64. 2 / 52.64. 2
libavdevice 52. 2. 0 / 52. 2. 0
libswscale 0.11. 0 / 0.11. 0
libpostproc 51. 2. 0 / 51. 2. 0
Hyper fast Audio and Video encoder
Any ideas as to why this would be happening?
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我做了很多研究并使用了 ffmpeg 的异步选项，我发现出现了唇形同步问题，因为音频被 libfaac 下采样，所以我更改了 --acodec 的选项来复制，这实际上意味着不要对其进行下采样并将其放入原始格式。
此后问题就消失了。
一些有助于了解 ffmpeg 更多信息的链接是：
1) 谈论 FFMPEG 的工作原理：http: //howto-pages.org/ffmpeg/
2）将视频转换为quicktime：http://ubuntuforums.org/archive/index.html php/t-387640.html
3) 在 UBUNTU 上安装 FFMPEG : http://ubuntuforums.org/showpost.php? p=6963607&postcount=360
I did a lot of research and played with async option of ffmpeg, I found out that the lip sync issue was occuring because of the fact that the audio was getting downsampled by libfaac so I changed the option of --acodec to copy which effectively means don't downsample it and put it in the raw format.
After this the issue was gone.
Couple of links which were kind of helpful in figuring out about ffmpeg more were:
1) Talks about how FFMPEG works: http://howto-pages.org/ffmpeg/
2) Converting video to quicktime: http://ubuntuforums.org/archive/index.php/t-387640.html
3) Installing FFMPEG on UBUNTU : http://ubuntuforums.org/showpost.php?p=6963607&postcount=360
当我遇到类似的问题时，您的答案也是对我来说效果很好的一种解决方案。然而，复制音轨对我来说不是一个选择，因为我希望它被压缩，而原始音轨可能有 384kbps 的音轨。
但你提到的重要的事情是下采样的问题。那，以及这个线程（http://doom10.org/index.php?topic=1639.0）让我思考并开始尝试 aac 编解码器。它被认为是实验性的，但对我来说效果很好！ -async、-vsync 什么也没做，但 -acodec aac -strictexperimental （为了 ffmpeg 不会警告你它是实验性的）创造了奇迹！强烈推荐此解决方案给任何有音频/视频同步问题并且无法复制音频且普通解决方案不起作用的人。 aac 是一个很棒的编解码器。我仍然会使用 libfaac 作为我的主要 aac 编解码器，因为 aac 是实验性的，但我很确定现在 acc 可以在生产中产生很好的结果并且保持一致。
Your answer is one solution that worked well for me, too, when I faced the similar problem. However, copying the audio track wasn't an option for me because I want it compressed, and originals might have 384kbps tracks.
But the important thing that you mentioned was the problem of downsampling. That, and this thread (http://doom10.org/index.php?topic=1639.0) got me thinking and into trying aac codec. It's deemed experimental, but it worked great for me! -async, -vsync did nothing, but -acodec aac -strict experimental (for ffmpeg not to warn you that it's experimental) did wonders! Highly recommend this solution to anyone who has audio/video sync problems and where copying the audio is not an option and ordinary solutions don't work. aac is a great codec. I'm still going to use libfaac as my main aac codec because aac is experimental but I am pretty sure now acc can produce great results in production and be consistent.