Using ffmpeg to record x11 screen & audio

Hi folks,

Attempting to do a screen capture (x11) including audio; say chrome is
playing a video clip and I want to capture a portion of the screen
along with the audio.

Quick search shows following example:

ffmpeg -f x11grab -probesize 32M -thread_queue_size 32 -i :0 \
-f sndio -thread_queue_size 32 -i snd/0 \
-codec:v libx264rgb -crf 0 -preset ultrafast \
-codec:a pcm_s16le \
raw.mkv

Unfortunately, play back of raw.mkv file using ffplay, there is no
audible audio.

Also, this command captures the entire screen. I am only interested in
capturing a portion of the screen, so my modified command is:

ffmpeg -f x11grab -s:0 640x480 -framerate 25 -i :0.0+100+50 -f sndio
-i snd/0 -crf 0 -preset ultrafast out.mp4

With this, the capture is at offset 100+50 and a size of 640x480.
Still no audio (unsurprisingly).

Can someone give me a hint as to how to get audio to record as well?

Cheers,
--patrick



ffmpeg details while playing raw.mkv
Input #0, matroska,webm, from '/tmp/raw.mkv': 0KB sq= 0B f=0/0
Metadata:
ENCODER : Lavf58.76.100
Duration: 00:00:49.33, start: 0.000000, bitrate: 10079 kb/s
Stream #0:0: Video: h264 (High 4:4:4 Predictive), gbrp(tv, gbr/unknown/unknown
, progressive), 1366x768, 29.25 fps, 29.25 tbr, 1k tbn, 58.50 tbc
(default) Metadata:
ENCODER : Lavc58.134.100 libx264rgb
DURATION : 00:00:49.333000000
Stream #0:1: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s (default)
Metadata:
ENCODER : Lavc58.134.100 pcm_s16le
DURATION : 00:00:48.981000000
29.27 A-V: -0.122 fd= 11 aq= 763KB vq= 5676KB sq= 0B f=0/0