我正在使用采集卡从另一台机器采集HDMI音频。
在我的主机上，arecord -l的输出如下：
**** List of CAPTURE Hardware Devices ****
Home directory not accessible: Permission denied
card 0: PCH [HDA Intel PCH], device 0: ALC283 Analog [ALC283 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: capture [ezcap U3 capture], device 0: USB Audio [USB Audio]
Subdevices: 1/1
Subdevice #0: subdevice #0
我使用的命令是：
sudo ffmpeg -f alsa -i hw:CARD=capture,DEV=0 -t 30 test.wav -loglevel debug
当我运行该命令时，日志似乎在"打开输入文件"处冻结，如下所示：
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libavresample 3. 7. 0 / 3. 7. 0
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
libpostproc 54. 7.100 / 54. 7.100
Splitting the commandline.
Reading option '-f' ... matched as option 'f' (force format) with argument 'alsa'.
Reading option '-i' ... matched as input url with argument 'hw:CARD=capture,DEV=0'.
Reading option '-t' ... matched as option 't' (record or transcode "duration" seconds of audio/video) with argument '30'.
Reading option 'test.wav' ... matched as output url.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Successfully parsed a group of options.
Parsing a group of options: input url hw:CARD=capture,DEV=0.
Applying option f (force format) with argument alsa.
Successfully parsed a group of options.
Opening an input file: hw:CARD=capture,DEV=0.
它将永远停留在那里，直到我按 Ctrl+C，然后日志继续如下：
[alsa @ 0x55c9f0eee8c0] interrupted
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, alsa, from 'hw:CARD=capture,DEV=0':
Duration: N/A, bitrate: 1536 kb/s
Stream #0:0, 0, 1/1000000: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Successfully opened the file.
Parsing a group of options: output url test.wav.
Applying option t (record or transcode "duration" seconds of audio/video) with argument 30.
Successfully parsed a group of options.
Opening an output file: test.wav.
File 'test.wav' already exists. Overwrite ? [y/N] y
[file @ 0x55c9f0f03280] Setting default whitelist 'file,crypto'
Successfully opened the file.
Stream mapping:
Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Finishing stream 0:0 without any data written to it.
detected 4 logical cores
[graph_0_in_0_0 @ 0x55c9f0f05dc0] Setting 'time_base' to value '1/48000'
[graph_0_in_0_0 @ 0x55c9f0f05dc0] Setting 'sample_rate' to value '48000'
[graph_0_in_0_0 @ 0x55c9f0f05dc0] Setting 'sample_fmt' to value 's16'
[graph_0_in_0_0 @ 0x55c9f0f05dc0] Setting 'channel_layout' to value '0x3'
[graph_0_in_0_0 @ 0x55c9f0f05dc0] tb:1/48000 samplefmt:s16 samplerate:48000 chlayout:0x3
[format_out_0_0 @ 0x55c9f0f060c0] Setting 'sample_fmts' to value 's16'
[AVFilterGraph @ 0x55c9f0f04be0] query_formats: 5 queried, 12 merged, 0 already done, 0 delayed
Output #0, wav, to 'test.wav':
Metadata:
ISFT : Lavf57.83.100
Stream #0:0, 0, 1/48000: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, stereo, s16, 1536 kb/s
Metadata:
encoder : Lavc57.107.100 pcm_s16le
size= 0kB time=00:00:00.00 bitrate=N/A speed= 0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (hw:CARD=capture,DEV=0):
Input stream #0:0 (audio): 0 packets read (0 bytes); 0 frames decoded (0 samples);
Total: 0 packets (0 bytes) demuxed
Output file #0 (test.wav):
Output stream #0:0 (audio): 0 frames encoded (0 samples); 0 packets muxed (0 bytes);
Total: 0 packets (0 bytes) muxed
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
0 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0x55c9f0f033e0] Statistics: 3 seeks, 3 writeouts
Exiting normally, received signal 2.
命令有什么问题？
我也有类似的问题。 我使用strace追踪它，发现ffmpeg无法打开USB捕获设备。 收到错误消息会很好，但它一直在尝试(永远(访问设备。
拔下并重新插入(即重置(捕获设备，现在一切都很好。