Alsa无法设置样本格式[FFMPEG] [英] Alsa cannot set sample format[FFMPEG]

问题描述

我正在尝试使用ffmpeg从Roland USB设备捕获pcm流，并用wav包装它.我正在使用的命令行如下:

I am trying to capture a pcm stream from a Roland USB device with ffmpeg and wrap it with wav. The command line I am using is the following:

ffmpeg -f alsa -acodec pcm_s32le -ac 2 -ar 48000 -i hw:2,0 out.wav

符合硬件设置.我还可以使用Audacity捕获流.问题是FFMPEG抛出无法设置样本格式错误" .对可能发生的事情以及如何解决此问题有任何想法吗?

Which comply with the settings of the hardware. I can also capture the stream with Audacity. The problem is that FFMPEG throws "cannot set sample format error". Any idea of what may be happening and how I can fix this?

谢谢.

FFMPEG输出

user@user:~$ ffmpeg -f alsa -acodec pcm_s32le -ac 2 -ar 48000 -i hw:2,0 out.wav
    ffmpeg version N-85548-g3390a2b Copyright (c) 2000-2017 the FFmpeg developers
      built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
      configuration: --enable-gpl --enable-libx264 --enable-libx265 --enable-libvpx --enable-libvorbis --enable-libopus --enable-ffplay
      libavutil      55. 61.100 / 55. 61.100
      libavcodec     57. 92.100 / 57. 92.100
      libavformat    57. 72.101 / 57. 72.101
      libavdevice    57.  7.100 / 57.  7.100
      libavfilter     6. 84.101 /  6. 84.101
      libswscale      4.  7.101 /  4.  7.101
      libswresample   2.  8.100 /  2.  8.100
      libpostproc    54.  6.100 / 54.  6.100
    [alsa @ 0x34b6780] cannot set sample format 0x10008 10 (Invalid argument)
    hw:2,0: Input/output error

记录输出:

user@user:~$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: PCH [HDA Intel PCH], device 0: ALC3236 Analog [ALC3236 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: DUOCAPTURE [DUO-CAPTURE], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

在Deimus的帮助下，我在记录中检查了卡的设置，并为FFMPEG使用了正确的行(请注意，我已更改了硬件上的捕获频率).

记录输出

user@user:~$ arecord --dump-hw-params -D hw:2,0
Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
HW Params of device "hw:2,0":
--------------------
ACCESS:  MMAP_INTERLEAVED RW_INTERLEAVED
FORMAT:  S24_3LE
SUBFORMAT:  STD
SAMPLE_BITS: 24
FRAME_BITS: 48
CHANNELS: 2
RATE: 44100
PERIOD_TIME: (1020 1981429)
PERIOD_SIZE: [45 87381]
PERIOD_BYTES: [270 524286]
PERIODS: [2 1024]
BUFFER_TIME: (2040 3962858)
BUFFER_SIZE: [90 174762]
BUFFER_BYTES: [540 1048572]
TICK_TIME: ALL
--------------------
arecord: set_params:1233: Sample format non available
Available formats:
- S24_3LE

正确的命令行

ffmpeg -f alsa -acodec pcm_s24le -ac 2 -ar 44100 -i hw:2,0 out.wav

推荐答案

使用arecord工具的--dump-hw-params选项检查支持的样本格式.

Use the --dump-hw-params option of arecord tool to check the supported sample formats.

arecord

Man 页面

然后，您可以使用ffmpeg的-sample_fmt选项指定格式，例如. s32

Then you can use the -sample_fmt option of ffmpeg to specficy the format eg. s32

ffmpeg的音频选项为此处

Audio options for ffmpeg are here

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