我有两个文件（一个是音频，一个是视频，都是 mp4），我想将它们合并为一个 mp4，而无需重新编码流。它们的持续时间相同（好吧，从技术上讲，一个比另一个长 0.05 秒，但对我的应用程序来说已经足够接近了）。我用来合并它们的命令是：
ffmpeg -i audio.mp4 -i video.mp4 -c:v copy -c:a copy test.mp4
当我在 VLC 播放器中播放时test.mp4，音频完全不同步。视频时长正确，但声音出现得太快，并且随着播放的进行，声音越来越不同步。但是，如果我使用 QuickTime 播放同一个文件，效果就完美了！
这是怎么回事？有没有办法确保无论使用哪种视频播放器都能正确播放，而无需重新编码流？
以下是该命令的完整输出：
% ffmpeg -i audio.mp4 -i video.mp4 -c:v copy -c:a copy test.mp4
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
built with Apple clang version 13.1.6 (clang-1316.0.21.2.5)
configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/5.0.1_2 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-neon
libavutil 57. 17.100 / 57. 17.100
libavcodec 59. 18.100 / 59. 18.100
libavformat 59. 16.100 / 59. 16.100
libavdevice 59. 4.100 / 59. 4.100
libavfilter 8. 24.100 / 8. 24.100
libswscale 6. 4.100 / 6. 4.100
libswresample 4. 3.100 / 4. 3.100
libpostproc 56. 3.100 / 56. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'audio.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp42mp41isomiso2
creation_time : 2022-07-24T22:23:15.000000Z
Duration: 00:00:27.17, start: 0.000000, bitrate: 129 kb/s
Stream #0:0[0x1](und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
creation_time : 2022-07-24T22:23:15.000000Z
handler_name : SoundHandler
vendor_id : [0][0][0][0]
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp42mp41isomiso2
creation_time : 2022-07-24T22:23:15.000000Z
Duration: 00:00:27.12, start: 0.000000, bitrate: 7662 kb/s
Stream #1:0[0x1](und): Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv), 1280x720, 7653 kb/s, SAR 1:1 DAR 16:9, 103.75 fps, 120 tbr, 12k tbn (default)
Metadata:
creation_time : 2022-07-24T22:23:15.000000Z
handler_name : VideoHandler
vendor_id : [0][0][0][0]
Output #0, mp4, to 'test.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: mp42mp41isomiso2
encoder : Lavf59.16.100
Stream #0:0(und): Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 7653 kb/s, 103.75 fps, 120 tbr, 12k tbn (default)
Metadata:
creation_time : 2022-07-24T22:23:15.000000Z
handler_name : VideoHandler
vendor_id : [0][0][0][0]
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
creation_time : 2022-07-24T22:23:15.000000Z
handler_name : SoundHandler
vendor_id : [0][0][0][0]
Stream mapping:
Stream #1:0 -> #0:0 (copy)
Stream #0:0 -> #0:1 (copy)
Press [q] to stop, [?] for help
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 29308, current: 29308; changing to 29309. This may result in incorrect timestamps in the output file.
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 111505, current: 111505; changing to 111506. This may result in incorrect timestamps in the output file.
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x148704fe0] Invalid timestamps stream=0, pts=128503, dts=128504, size=6321
[mp4 @ 0x148708150] Invalid DTS: 128504 PTS: 128503 in output stream 0:0, replacing by guess
[mp4 @ 0x148708150] Non-monotonous DTS in output stream 0:0; previous: 128504, current: 128504; changing to 128505. This may result in incorrect timestamps in the output file.
frame= 2814 fps=0.0 q=-1.0 Lsize= 25817kB time=00:00:27.16 bitrate=7784.7kbits/s speed=1.5e+03x
video:25340kB audio:424kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.201361%