[FFmpeg-user] Cannot set ALSA buffer size (Invalid argument) during capture

[Marco Paolieri]

On Sun, Nov 26, 2017 at 2:13 PM, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> I tried to compile ffmpeg 0.6.7 from GitHub, but without success; it
>> gives the error:
>>
>> libavcodec/vaapi_mpeg4.c:89:73: error: implicit declaration of
>> function ‘ff_h263_get_gob_height’; did you mean ‘ff_h261_encode_init’?
>>
>> Probably, I'm missing some old dependency?
>
> Unlikely, but try --disable-vaapi

It worked, but then I hit:

  ffserver.c: In function ‘rtsp_cmd_describe’:
  ffserver.c:2987:5: error: implicit declaration of function
‘ff_url_split’ [-Werror=implicit-function-declaration]

So I tried to add '--disable-ffserver'; and it finished!
Now, it gives a different error:

  ~/bin$ ./ffmpeg -f alsa -i hw:1,0 -t 30 out.wav
  FFmpeg version 0.6.7, Copyright (c) 2000-2010 the FFmpeg developers
   built on Nov 26 2017 18:07:01 with gcc 7.2.0
   configuration: --disable-vaapi --disable-ffserver
--prefix=/home/marco/ffmpeg_build
--extra-cflags=-I/home/marco/ffmpeg_build/include
--bindir=/home/marco/bin
   libavutil     50.15. 1 / 50.15. 1
   libavcodec    52.72. 2 / 52.72. 2
   libavformat   52.64. 2 / 52.64. 2
   libavdevice   52. 2. 0 / 52. 2. 0
   libswscale     0.11. 0 /  0.11. 0
  [alsa @ 0x558ad41be420]cannot set channel count to 1 (Invalid argument)
  hw:1,0: Input/output error

This gives maybe more insight! The USB capture card is stereo (two RCA
connectors), but I'm capturing from a mono source (only one RCA
connector is plugged into the USB device). Is there some additional
option I should pass to ffmpeg? With qv4l2, I simply get audio only in
one channel (right).

> Please do not top-post here, Carl Eugen
Apologies; I wasn't aware of the etiquette :-)

-- Marco