Estou usando o ffmpeg para dividir o áudio de um arquivo de vídeo, convertendo-o em wav e, em seguida, recombinando-o com o vídeo. Quando faço isso, o novo vídeo tem quadros pretos no começo.
Aqui estão os comandos que estou executando:
ffmpeg -i orig.mp4 orig-sound.wav
ffmpeg -i orig.mp4 -i orig-sound.wav -map 0:0 -map 1:0 -vcodec copy new.mp4
Eu notei que se eu adicionar um -itsoffset -0.5 quando recombinar, então os quadros pretos não estão presentes, mas eu não entendo porque isso funciona ou porque é necessário.
ffmpeg -itsoffset -0.5 -i orig.mp4 -i orig-sound.wav -map 0:0 -map 1:0 -vcodec copy new.mp4
Mais informações: isso acontece apenas para alguns vídeos.
Saída do comando dividido
Running command: ffmpeg -i shortvideo.mp4 -y /var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-13uwbwy.wav
ffmpeg version 2.6.2 Copyright (c) 2000-2015 the FFmpeg developers
built with Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn)
configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
libavutil 54. 20.100 / 54. 20.100
libavcodec 56. 26.100 / 56. 26.100
libavformat 56. 25.101 / 56. 25.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 11.102 / 5. 11.102
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'shortvideo.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.25.101
Duration: 00:01:15.72, start: 0.072562, bitrate: 171 kb/s
Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 800x600, 40 kb/s, 24.01 fps, 24 tbr, 12288 tbn, 48 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 22050 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
handler_name : SoundHandler
Output #0, wav, to '/var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-13uwbwy.wav':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
ISFT : Lavf56.25.101
Stream #0:0(und): Audio: pcm_s16le ([1][0][0][0] / 0x0001), 22050 Hz, stereo, s16, 705 kb/s (default)
Metadata:
handler_name : SoundHandler
encoder : Lavc56.26.100 pcm_s16le
Stream mapping:
Stream #0:1 -> #0:0 (aac (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
size= 6524kB time=00:01:15.74 bitrate= 705.6kbits/s
video:0kB audio:6524kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.001168%
Saída de mesclagem
Running command: ffmpeg -i shortvideo.mp4 -i /var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-ou67bd.wav -map 0:0 -map 1:0 -vcodec copy -ab 127166 /var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-1lafn4z.mp4
ffmpeg version 2.6.2 Copyright (c) 2000-2015 the FFmpeg developers
built with Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn)
configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
libavutil 54. 20.100 / 54. 20.100
libavcodec 56. 26.100 / 56. 26.100
Running command: ffmpeg -i shortvideo.mp4 -y /var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-13uwbwy.wav
libavformat 56. 25.101 / 56. 25.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 11.102 / 5. 11.102
libavresample 2. 1. 0 / 2. 1. 0
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'shortvideo.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.25.101
Duration: 00:01:15.72, start: 0.072562, bitrate: 171 kb/s
Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 800x600, 40 kb/s, 24.01 fps, 24 tbr, 12288 tbn, 48 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 22050 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
handler_name : SoundHandler
Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, wav, from '/var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-ou67bd.wav':
Duration: 00:01:15.74, bitrate: 705 kb/s
Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 22050 Hz, 2 channels, s16, 705 kb/s
Output #0, mp4, to '/var/folders/rr/x5blbrq14yj6zwlj5_y2y5gh0000gp/T/11555-44766-1lafn4z.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf56.25.101
Stream #0:0(und): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 800x600, q=2-31, 40 kb/s, 24.01 fps, 24 tbr, 12288 tbn, 12288 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1: Audio: aac (libvo_aacenc) ([64][0][0][0] / 0x0040), 22050 Hz, stereo, s16, 127 kb/s
Metadata:
encoder : Lavc56.26.100 libvo_aacenc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (libvo_aacenc))
Press [q] to stop, [?] for help
[mp4 @ 0x7fbf0c826e00] Packet with invalid duration -2654 in stream 0164.3kbits/s
frame= 1807 fps=0.0 q=-1.0 Lsize= 1585kB time=00:01:15.76 bitrate= 171.4kbits/s
video:376kB audio:1177kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.046465%
1/1 videos completed...
Success: shortvideo.mp4
Processed 1623247 bytes in 3.064000129699707 seconds, at 0.5297803300547149 MB/sec