When I attempt to sync a .mov video with an .m4a audio file using ffmpeg like so
ffmpeg -ss 00:00:2 -i test.m4a -i test.mov -c:v copy -c:a aac -strict experimental output.mp4
it works like a charm. But right now I've recorded a usability test video using adobe XD, and it returned an .mp4 (MPEG-4) video and I manually recorded the audio using quicktimre returning a .m4a audio file.
Trying to merge them using ffmpeg is returning a video without any audio:
ffmpeg -i video.mp4 -i audio.m4a -c:v copy -c:a aac -strict experimental output.mp4
ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1_1 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gpl --enable-libmp3lame --enable-libopus --enable-libsnappy --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-opencl --enable-videotoolbox
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
Metadata:
major_brand : qt
minor_version : 0
compatible_brands: qt
creation_time : 2019-07-31T14:43:18.000000Z
com.apple.quicktime.make: Apple
com.apple.quicktime.model: MacBookPro15,1
com.apple.quicktime.software: Mac OS X 10.14.5 (18F203)
com.apple.quicktime.creationdate: 2019-07-31T17:43:17+0300
Duration: 00:03:46.05, start: 0.000000, bitrate: 498 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 374x812 [SAR 1:1 DAR 187:406], 390 kb/s, 60 fps, 60 tbr, 6k tbn, 12k tbc (default)
Metadata:
creation_time : 2019-07-31T14:43:18.000000Z
handler_name : Core Media Video
encoder : H.264
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, stereo, fltp, 0 kb/s (default)
Metadata:
creation_time : 2019-07-31T14:43:18.000000Z
handler_name : Core Media Audio
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'audio.m4a':
Metadata:
major_brand : M4A
minor_version : 0
compatible_brands: M4A mp42isom
creation_time : 2019-07-31T14:47:26.000000Z
iTunSMPB : 00000000 00000840 00000000 00000000009DFBC0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Duration: 00:03:54.78, start: 0.047891, bitrate: 225 kb/s
Stream #1:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 224 kb/s (default)
Metadata:
creation_time : 2019-07-31T14:47:26.000000Z
handler_name : Core Media Audio
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[aac @ 0x7fb5a4806a00] Too many bits 16384.000000 > 12288 per frame requested, clamping to max
Output #0, mp4, to 'output.mp4':
Metadata:
major_brand : qt
minor_version : 0
compatible_brands: qt
com.apple.quicktime.creationdate: 2019-07-31T17:43:17+0300
com.apple.quicktime.make: Apple
com.apple.quicktime.model: MacBookPro15,1
com.apple.quicktime.software: Mac OS X 10.14.5 (18F203)
encoder : Lavf58.20.100
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 374x812 [SAR 1:1 DAR 187:406], q=2-31, 390 kb/s, 60 fps, 60 tbr, 12k tbn, 6k tbc (default)
Metadata:
creation_time : 2019-07-31T14:43:18.000000Z
handler_name : Core Media Video
encoder : H.264
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 8000 Hz, stereo, fltp, 96 kb/s (default)
Metadata:
creation_time : 2019-07-31T14:43:18.000000Z
handler_name : Core Media Audio
encoder : Lavc58.35.100 aac
frame=13563 fps=0.0 q=-1.0 Lsize= 10903kB time=00:03:46.08 bitrate= 395.1kbits/s speed= 916x
video:10699kB audio:10kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.805767%
How can I get around this limitation?
The Adobe XD video has an audio stream in it so ffmpeg has picked it.
Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Use -map to explicitly select audio source.
ffmpeg -i video.mp4 -i audio.m4a -map 0:v -map 1:a -c:v copy -c:a aac -strict experimental output.mp4