bit perfect audio on linux

This seems like a reasonable goal if you've got the right hardware, Right?



ALSA

With aplay -L you'll want to see that you have a iec958 (optical out) device.

iec958:CARD=PCH,DEV=0
    HDA Intel PCH, ALC892 Digital
    IEC958 (S/PDIF) Digital Audio Output

verification

Check to see what format and bitrate is actually being used by the device:

~ cat /proc/asound/card0/pcm1p/sub0/hw_params

access: MMAP_INTERLEAVED
format: S16_LE
subformat: STD
channels: 2
rate: 48000 (48000/1)
period_size: 44100
buffer_size: 88200

head-fi bit-perfect-audio-from-linux

configure Audacious

configure DeaDBeeF

iecset - IEC958 controls

This seems like an interesting tool to dump optical output information, even if it doesn't appear to do much in consumer mode.

iecset -Dhw:1

quake soundtrack

The original quake soundrack was recorded to the cd with pre-emphasis applied to the tracks. This means that the higher frequencies would be boosted prior to writing the tracks, resulting in a better signal to noise ratio. If you use a dedicaated cd device or direct line, the emphasis bit will be detected, boost removed, and you hear what you expect. Unfortuantely, if you read the tracks as data for copying to flac, the boost will persist and you'll have a heavy high frequency version of the soundtrack. This is well handled with SoX but it took me an embarrasingly long amount of time actually learn emphasis existed in spite of decades of listening to this cd.

quake soundtrack solutions - source of the enlightenment.