ffmpeg：音频和视频组合时显着滞后和音频同步不佳

我正在尝试将来自Raspberry Pi的音频和视频结合起来进行流式传输。音频引导视频几秒钟，无论是流输出还是将其写入文件。

命令行：

raspivid -o - -t 0 -n -w 1280 -h 720 -fps 25 | ffmpeg -report -probesize 32000 -thread_queue_size 1024 -y -f h264 -r 25 -framerate 25 -i - -thread_queue_size 512 -f alsa -ac 1 -channel_layout mono -i hw:1 -vcodec copy -acodec mp3 -f mpegts udp://44.0.0.95:1234

ffmpeg报告/日志：

ffmpeg started on 2015-06-15 at 19:14:26
Report written to "ffmpeg-20150615-191426.log"
Command line:
ffmpeg -report -probesize 32000 -thread_queue_size 1024 -y -f h264 -r 25 -framerate 25 -i - -thread_queue_size 512 -f alsa -ac 1 -channel_layout mono -i hw:1 -vcodec copy -acodec mp3 -f mpegts udp://44.0.0.95:1234
ffmpeg version N-72834-gfd004e1 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.6 (Debian 4.6.3-14+rpi1)
  configuration: --enable-libmp3lame
  libavutil      54. 27.100 / 54. 27.100
  libavcodec     56. 41.100 / 56. 41.100
  libavformat    56. 36.100 / 56. 36.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
Splitting the commandline.
Reading option '-report' ... matched as option 'report' (generate a report) with argument '1'.
Reading option '-probesize' ... matched as AVOption 'probesize' with argument '32000'.
Reading option '-thread_queue_size' ... matched as option 'thread_queue_size' (set the maximum number of queued packets from the demuxer) with argument '1024'.
Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'h264'.
Reading option '-r' ... matched as option 'r' (set frame rate (Hz value, fraction or abbreviation)) with argument '25'.
Reading option '-framerate' ... matched as AVOption 'framerate' with argument '25'.
Reading option '-i' ... matched as input file with argument '-'.
Reading option '-thread_queue_size' ... matched as option 'thread_queue_size' (set the maximum number of queued packets from the demuxer) with argument '512'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'alsa'.
Reading option '-ac' ... matched as option 'ac' (set number of audio channels) with argument '1'.
Reading option '-channel_layout' ... matched as option 'channel_layout' (set channel layout) with argument 'mono'.
Reading option '-i' ... matched as input file with argument 'hw:1'.
Reading option '-vcodec' ... matched as option 'vcodec' (force video codec ('copy' to copy stream)) with argument 'copy'.
Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'mp3'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'mpegts'.
Reading option 'udp://44.0.0.95:1234' ... matched as output file.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option report (generate a report) with argument 1.
Applying option y (overwrite output files) with argument 1.
Successfully parsed a group of options.
Parsing a group of options: input file -.
Applying option thread_queue_size (set the maximum number of queued packets from the demuxer) with argument 1024.
Applying option f (force format) with argument h264.
Applying option r (set frame rate (Hz value, fraction or abbreviation)) with argument 25.
Successfully parsed a group of options.
Opening an input file: -.
[h264 @ 0x12a83c0] Before avformat_find_stream_info() pos: 0 bytes read:4096 seeks:0
[h264 @ 0x12a83c0] Probe buffer size limit of 32000 bytes reached
[h264 @ 0x12a83c0] Stream #0: not enough frames to estimate rate; consider increasing probesize
[h264 @ 0x12a83c0] decoding for stream 0 failed
[h264 @ 0x12a83c0] After avformat_find_stream_info() pos: 34816 bytes read:53248 seeks:0 frames:3
Input #0, h264, from 'pipe:':
  Duration: N/A, bitrate: N/A
    Stream #0:0, 3, 1/1200000: Video: h264 (High), yuv420p, 1280x720, 25 fps, 25 tbr, 1200k tbn, 50 tbc
Successfully opened the file.
Parsing a group of options: input file hw:1.
Applying option thread_queue_size (set the maximum number of queued packets from the demuxer) with argument 512.
Applying option f (force format) with argument alsa.
Applying option ac (set number of audio channels) with argument 1.
Applying option channel_layout (set channel layout) with argument mono.
Successfully parsed a group of options.
Opening an input file: hw:1.
[alsa @ 0x12cee80] All info found
Input #1, alsa, from 'hw:1':
  Duration: N/A, start: 1434392072.070301, bitrate: 768 kb/s
    Stream #1:0, 1, 1/1000000: Audio: pcm_s16le, 48000 Hz, mono, s16, 768 kb/s
Successfully opened the file.
Parsing a group of options: output file udp://44.0.0.95:1234.
Applying option vcodec (force video codec ('copy' to copy stream)) with argument copy.
Applying option acodec (force audio codec ('copy' to copy stream)) with argument mp3.
Applying option f (force format) with argument mpegts.
Successfully parsed a group of options.
Opening an output file: udp://44.0.0.95:1234.
Matched encoder 'libmp3lame' for codec 'mp3'.
Successfully opened the file.
detected 4 logical cores
[graph 0 input from stream 1:0 @ 0x12a82a0] Setting 'time_base' to value '1/48000'
[graph 0 input from stream 1:0 @ 0x12a82a0] Setting 'sample_rate' to value '48000'
[graph 0 input from stream 1:0 @ 0x12a82a0] Setting 'sample_fmt' to value 's16'
[graph 0 input from stream 1:0 @ 0x12a82a0] Setting 'channel_layout' to value '0x4'
[graph 0 input from stream 1:0 @ 0x12a82a0] tb:1/48000 samplefmt:s16 samplerate:48000 chlayout:0x4
[audio format for output stream 0:1 @ 0x12a0390] Setting 'sample_fmts' to value 's32p|fltp|s16p'
[audio format for output stream 0:1 @ 0x12a0390] Setting 'sample_rates' to value '44100|48000|32000|22050|24000|16000|11025|12000|8000'
[audio format for output stream 0:1 @ 0x12a0390] Setting 'channel_layouts' to value '0x4|0x3'
[audio format for output stream 0:1 @ 0x12a0390] auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed_anull_0' and the filter 'audio format for output stream 0:1'
[AVFilterGraph @ 0x1320b60] query_formats: 4 queried, 6 merged, 3 already done, 0 delayed
[auto-inserted resampler 0 @ 0x1321c60] ch:1 chl:mono fmt:s16 r:48000Hz -> ch:1 chl:mono fmt:s16p r:48000Hz
[mpegts @ 0x12bdbf0] muxrate VBR, pcr every 2 pkts, sdt every 200, pat/pmt every 40 pkts
Output #0, mpegts, to 'udp://44.0.0.95:1234':
  Metadata:
    encoder         : Lavf56.36.100
    Stream #0:0, 0, 1/90000: Video: h264, yuv420p, 1280x720, q=2-31, 25 fps, 25 tbr, 90k tbn, 25 tbc
    Stream #0:1, 0, 1/90000: Audio: mp3 (libmp3lame), 48000 Hz, mono, s16p
    Metadata:
      encoder         : Lavc56.41.100 libmp3lame
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #1:0 -> #0:1 (pcm_s16le (native) -> mp3 (libmp3lame))
frame=   11 fps=0.0 q=-1.0 size=     276kB time=00:00:00.44 bitrate=5130.7kbits/s    
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frame= 1687 fps= 25 q=-1.0 size=   32932kB time=00:01:07.48 bitrate=3997.9kbits/s    
frame= 1699 fps= 25 q=-1.0 size=   33175kB time=00:01:07.96 bitrate=3999.0kbits/s    
frame= 1712 fps= 25 q=-1.0 size=   33507kB time=00:01:08.48 bitrate=4008.3kbits/s    
frame= 1724 fps= 25 q=-1.0 size=   33797kB time=00:01:08.96 bitrate=4014.9kbits/s    
frame= 1737 fps= 25 q=-1.0 size=   34091kB time=00:01:09.48 bitrate=4019.5kbits/s    
frame= 1750 fps= 25 q=-1.0 size=   34451kB time=00:01:10.00 bitrate=4031.8kbits/s    
frame= 1763 fps= 25 q=-1.0 size=   34750kB time=00:01:10.52 bitrate=4036.7kbits/s    
frame= 1775 fps= 25 q=-1.0 size=   35010kB time=00:01:11.00 bitrate=4039.5kbits/s    
[libmp3lame @ 0x1320770] Trying to remove 47 more samples than there are in the queue
frame= 1779 fps= 25 q=-1.0 Lsize=   35116kB time=00:01:11.28 bitrate=4035.7kbits/s    
video:31803kB audio:557kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 8.515517%
Input file #0 (pipe:):
  Input stream #0:0 (video): 1779 packets read (32566370 bytes); 
  Total: 1779 packets (32566370 bytes) demuxed
Input file #1 (hw:1):
  Input stream #1:0 (audio): 57720 packets read (6842992 bytes); 57720 frames decoded (3421496 samples); 
  Total: 57720 packets (6842992 bytes) demuxed
Output file #0 (udp://44.0.0.95:1234):
  Output stream #0:0 (video): 1779 packets muxed (32566370 bytes); 
  Output stream #0:1 (audio): 2970 frames encoded (3421440 samples); 2971 packets muxed (570432 bytes); 
  Total: 4750 packets (33136802 bytes) muxed
57720 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0x1321210] Statistics: 0 seeks, 25491 writeouts
[AVIOContext @ 0x12a7e40] Statistics: 35211617 bytes read, 0 seeks
Received signal 2: terminating.

这就是我的建议：如果你能够通过使用a来测试你的相机的输出同步 raspvid 预览窗口，你发现相机落后，然后我会说相机的h264编码器是责任。但是，如果它同步，则FFmpeg在管道输入上执行一个数字。

如果相机的h264编码器出现问题 并且音频后面的视频滞后是一致的持续时间（即，每次观察到2.5秒的延迟），你可以添加一个 -itsoffset 音频输入的参数，以延迟该持续时间。例如：

raspivid -o - -t 0 -n -w 1280 -h 720 -fps 25 | \
ffmpeg -report -y \
-f h264 -r 25 -i - \
-itsoffset 2.5 -f alsa -ac 1 -i hw:1 \
-vcodec copy -acodec libmp3lame -ac 1 -ar 44100 -b:a 128k \
-f mpegts udp://44.0.0.95:1234

如果相机的预览输出没有延迟 ，然后我建议安装相机的V4L2驱动程序，这样你的FFmpeg命令就可以直接从相机中取出帧。

ffmpeg -report -y \
-f v4l2 -input_format h264 -r 25 -video_size 1280x720 -i /dev/video0 \
-f alsa -ac 1 -i hw:1 \
-vcodec copy -acodec libmp3lame -ac 1 -ar 44100 -b:a 128k \
-f mpegts udp://44.0.0.95:1234

然而，根据我在网上收集的内容，人们对这款相机的V4L2驱动程序的性能抱怨，所以你最终可能会坚持使用你所知道的魔鬼并使用它 -itsoffset 关于音频输入无论如何。

命令说明：我已经删除了 probesize 您指定输入格式和帧速率的命令选项。此外，您不应同时指定两者 -r 25 （将“帧速率”强制为指定值） 和 -framerate 25 （它会尝试使用'原生'输入帧速率）。我离开了 -r 25 因为我发现它对于实时视频输入效果更好。 MP3编码器设置更具体，因此FFmpeg不必“猜测”它们。 -thread_queue_size 修剪了params以获得行长，因此如果绝对必要，您可以将它们重新添加。

尝试在rtp：//127.0.0.1：1235上重新播放音频，并将视频合并到mp4容器中。