我在将未压缩的视频转换为 mp4 格式并使用 AAC 音频时遇到了问题。我没有收到任何错误，但 Windows Media PLayer 的输出文件中的视频无法播放音频（其他播放器可以很好地处理这个问题，但通常 WMP 不会对我的其他 MP4 产生问题，所以我仍然觉得这里出了问题）。这是我的完整命令：
ffmpeg -i uncompressed.avi -s 426x240 -pix_fmt yuv420p -c:v libx264 -preset:v veryslow -profile:v main -crf:v 27 -movflags +faststart -c:a libfdk_aac -b:a 128k -t 00:00:10 output.mp4
输出结果如下：
ffmpeg version N-55064-g3cd8aaa Copyright (c) 2000-2013 the FFmpeg developers
built on Jul 29 2013 12:59:12 with gcc 4.8.0 (GCC)
configuration: --arch=x86_64 --target-os=mingw32 --cross-prefix=/home/dominic/GitHub/ffmpeg-windows-build-helpers/sandbox/mingw-w64-x86_64/bin/x86_64-w64-mingw32- --pkg-config=pkg-config --enable-gpl --enable-libsoxr --enable-libx264 --enable-avisynth --enable-libxvid --enable-libmp3lame --enable-version3 --enable-zlib --enable-librtmp --enable-libvorbis --enable-libtheora --enable-libspeex --enable-libopenjpeg --enable-gnutls --enable-libgsm --enable-libfreetype --enable-fontconfig --enable-libass --enable-libutvideo --enable-libopus --disable-w32threads --enable-frei0r --enable-filter=frei0r --enable-libvo-aacenc --enable-bzlib --enable-libxavs --extra-cflags=-DPTW32_STATIC_LIB --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-libschroedinger --enable-libbluray --enable-libvpx --enable-libilbc --enable-static --disable-shared --enable-nonfree --enable-libfdk-aac --enable-runtime-cpudetect
libavutil 52. 40.100 / 52. 40.100
libavcodec 55. 19.100 / 55. 19.100
libavformat 55. 12.102 / 55. 12.102
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 81.103 / 3. 81.103
libswscale 2. 4.100 / 2. 4.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, avi, from 'uncompressed.avi':
Metadata:
date : 2012-04-16T16:02:12.00409-07:00
Duration: 00:02:22.93, start: 0.000000, bitrate: 1199367 kb/s
Stream #0:0: Video: rawvideo, bgr24, 1920x1080, 23.98 tbr, 23.98 tbn, 23.98 tbc
Stream #0:1: Audio: pcm_f32le ([3][0][0][0] / 0x0003), 96000 Hz, stereo, flt, 6144 kb/s
[libx264 @ 000000000038f580] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
[libx264 @ 000000000038f580] profile Main, level 2.2
[libx264 @ 000000000038f580] 264 - core 133 r2339 585324f - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - http://www.videolan.org/x264.html - options: cabac=1 ref=16 deblock=1:0:0 analyse=0x1:0x131 me=umh subme=10 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=24 chroma_me=1 trellis=2 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=8 b_pyramid=2 b_adapt=2 b_bias=0 direct=3 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=23 scenecut=40 intra_refresh=0 rc_lookahead=60 rc=crf mbtree=1 crf=27.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output.mp4':
Metadata:
date : 2012-04-16T16:02:12.00409-07:00
encoder : Lavf55.12.102
Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 426x240, q=-1--1, 24k tbn, 23.98 tbc
Stream #0:1: Audio: aac (libfdk_aac) ([64][0][0][0] / 0x0040), 96000 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo -> libx264)
Stream #0:1 -> #0:1 (pcm_f32le -> libfdk_aac)
Press [q] to stop, [?] for help
frame= 53 fps=0.0 q=0.0 size= 0kB time=00:00:02.84 bitrate= 0.1kbits/s
frame= 98 fps= 97 q=32.0 size= 23kB time=00:00:04.76 bitrate= 38.8kbits/s
frame= 151 fps=100 q=32.0 size= 64kB time=00:00:06.68 bitrate= 78.5kbits/s
frame= 200 fps= 99 q=32.0 size= 105kB time=00:00:08.60 bitrate= 99.7kbits/s
[mp4 @ 00000000023d8e20] Starting second pass: moving header on top of the file
frame= 240 fps= 87 q=-1.0 Lsize= 244kB time=00:00:10.00 bitrate= 199.8kbits/s
video:77kB audio:157kB subtitle:0 global headers:0kB muxing overhead 4.142690%
[libx264 @ 000000000038f580] frame I:2 Avg QP:24.64 size: 8447
[libx264 @ 000000000038f580] frame P:45 Avg QP:29.82 size: 686
[libx264 @ 000000000038f580] frame B:193 Avg QP:35.11 size: 159
[libx264 @ 000000000038f580] consecutive B-frames: 0.8% 0.0% 2.5% 26.7% 22.9% 15.0% 11.7% 16.7% 3.8%
[libx264 @ 000000000038f580] mb I I16..4: 41.6% 0.0% 58.4%
[libx264 @ 000000000038f580] mb P I16..4: 0.2% 0.0% 0.7% P16..4: 12.0% 3.7% 5.8% 0.8% 0.3% skip:76.4%
[libx264 @ 000000000038f580] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 8.5% 1.5% 0.9% direct: 0.3% skip:88.8% L0:42.5% L1:50.5% BI: 7.0%
[libx264 @ 000000000038f580] direct mvs spatial:95.9% temporal:4.1%
[libx264 @ 000000000038f580] coded y,uvDC,uvAC intra: 76.0% 40.8% 12.1% inter: 1.6% 0.4% 0.0%
[libx264 @ 000000000038f580] i16 v,h,dc,p: 25% 29% 6% 39%
[libx264 @ 000000000038f580] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 13% 4% 9% 13% 12% 14% 11% 14%
[libx264 @ 000000000038f580] i8c dc,h,v,p: 21% 48% 21% 10%
[libx264 @ 000000000038f580] Weighted P-Frames: Y:2.2% UV:2.2%
[libx264 @ 000000000038f580] ref P L0: 48.5% 11.1% 11.4% 4.7% 4.1% 5.3% 3.6% 1.9% 1.6% 1.5% 0.9% 1.1% 0.9% 1.3% 1.1% 1.1%
[libx264 @ 000000000038f580] ref B L0: 77.3% 6.0% 5.8% 2.5% 2.5% 2.1% 1.3% 0.5% 0.6% 0.3% 0.3% 0.4% 0.2% 0.2% 0.2%
[libx264 @ 000000000038f580] ref B L1: 93.9% 6.1%
[libx264 @ 000000000038f580] kb/s:62.65
我收到的唯一警告是它猜测了音频的通道布局。但是，它猜对了，所以我看不出这怎么会是问题所在：
我尝试过的事情：
- 使用
libvo_aacencandaac(与-strict experimental)...结果相同 - 在可自由分发的版本（无需编译
--enable-nonfree）上厌倦了上述两种情况，从以下位置下载这里而不是我自己构建的...结果相同 - 使用 ...audio 编码相同的输入文件
libvorbis效果很好
我不知所措。事实上，vorbis 编码器工作正常，这让我认为输入文件没有问题。但是，我不明白为什么 AAC 会因此而受阻。有什么想法我哪里做错了吗？
更新：ffprobe以下是有问题的文件 的输出：
ffprobe version N-54933-g1af9211 Copyright (c) 2007-2013 the FFmpeg developers
built on Jul 25 2013 18:05:50 with gcc 4.7.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
libavutil 52. 40.100 / 52. 40.100
libavcodec 55. 19.100 / 55. 19.100
libavformat 55. 12.102 / 55. 12.102
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 81.103 / 3. 81.103
libswscale 2. 4.100 / 2. 4.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
date : 2012-04-16T16:02:12.00409-07:00
encoder : Lavf55.12.102
Duration: 00:00:10.03, start: 0.021333, bitrate: 199 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 426x240, 63 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 96000 Hz, stereo, fltp, 128 kb/s
Metadata:
handler_name : SoundHandler
答案1
好的，这里的问题似乎是采样率。音频以 96 kHz 编码，显然 Windows Media Player 不支持。当我将-ar 48000采样率设置为 48 kHz 时，音频播放完美。无论如何，96 kHz 对于网络视频来说可能有点过分了。感谢所有提供帮助的人。