в котором плеере я могу играть выходной видеофайл recordMyDesktop, который имеет расширение .pcm?

Используя vlc:

sudo apt-get install vlc

recordmydesktop создает a out.ogv

Поэтому:

vlc out.ogv

В случае использования файла PCM

vlc audio.pcm

Или откройте свойства для audio.pcm в Вашем файловом менеджере и выборе Открывают withVLC

Пример

% recordmydesktop
Initial recording window is set to:
X:0   Y:0    Width:1920    Height:1200
Adjusted recording window is set to:
X:0   Y:0    Width:1920    Height:1200
Your window manager appears to be GNOME Shell


Detected compositing window manager.
Reverting to full screen capture at every frame.
To disable this check run with --no-wm-check
(though that is not advised, since it will probably produce faulty results).

Initializing...
Buffer size adjusted to 4096 from 4096 frames.
Opened PCM device default
Recording on device default is set to:
1 channels at 22050Hz
Capturing!

^C
*********************************************

Cached 17 MB, from 1344 MB that were received.
Average cache compression ratio: 98.7 %

*********************************************
Saved 153 frames in a total of 152 requests
Shutting down.....
STATE:ENCODING
Encoding started!
This may take several minutes.
Pressing Ctrl-C will cancel the procedure (resuming will not be possible, but
any portion of the video, which is already encoded won't be deleted).
Please wait...
Output file: out.ogv
[101%] 
Encoding finished!
Wait a moment please...

Done.
Written 2631681 bytes
(2526038 of which were video data and 105643 audio data)

Cleanning up cache...
Done!!!
Goodbye!