Using Audio jacks¶
The 335x provides an ALSA driver in the kernel for recording and playing audio files.
To learn more about ALSA you can read up on it here: http://www.alsa-project.org/main/index.php/Main_Page
Using ALSA tools to record/play wav files¶
# Unmute the microphone amixer set PCM 100 on || echo "Unable to set mixer control for PCM" # Record in dat file format for 3 seconds. arecord -f dat -d 3 > test.wav || echo "Unable to run arecord"
# Unmute the speaker amixer set PCM 100 on || echo "Unable to set mixer control for PCM" # Playback wav file aplay test.wav || echo "aplay failed"
Integrating with Application¶
Gstreamer is one possibility for integrating sound into your application.
# Record into mp4 format until canceled gst-launch -e alsasrc ! 'audio/x-raw-int,rate=(int)44100,channels=(int)2' ! queue ! ffenc_aac bitrate=128000 ! qtmux ! filesink location=audio_aac.mp4
gst-launch filesrc location=audio_aac.mp4 ! qtdemux ! ffdec_aac ! alsasink
If there are issues setting mixer levels with the ALSA tools, you can set the volume directly in the gst-launch command with the 'volume' element. The volume is set on a scale from '0' to '1' with '1' being 100% of the input level. Here's the same gst-launch playback command with the volume set to 50% of the original level.
gst-launch filesrc location=audio_aac.mp4 ! qtdemux ! ffdec_aac ! volume volume='0.5' ! alsasink
Note: gst-inspect can be used to identify what pipelines are available.
Read up on the following for more info on gstreamer: http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/
Audo playback linux applications¶
The following programs should be available to install via
- vlc - 126.96.36.199-r0.6 - Video player and streamer - davinci edition
- mplayer - 0.0+1.0rc3+svnr32735-r27.6 - Open Source multimedia player.
- madplay - 0.15.2b-r0.6 - Madplay is a command-line MPEG audio decoder and player
- ffmpeg - 2:0.6.1+r17.1+gitr0+0b32da90f893b3e04ead18a546252e241a6a0988-r17.1.6 - FFmpeg is a complete solution to record, convert and stream audio and video
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