[alsa-devel] alsa compliance test: H340 (USB audio) playback / capture rate asymmetry bug?

[Hin-Tak Leung]

I am using Takashi Iwai's tree grafted onto mainline as DKMS ( as in
https://github.com/HinTak/sound-usb-dkms ).

Running the alsa compliance test 
commit f6167eb77d038b5b7a0d39645e7f2ae7fee6fdc0 (origin/stabilize-12464.B, origin/release-R78-12499.B)

Capture all passed, but play back failed a couple, regarding the sample rate.
It is a small head set with stereo head phone and a mic.
ID 046d:0a38 Logitech, Inc. Headset H340

The question is, for such a cheap headset, why would the playback rate and the capture rate to be different? For many applications/ usages, with a device that's most capture and playback capable, we would like the rates to agree - both pass, or both fail in the same direction?

Is this a hardware or software issue? Or, somebody suggested, I haven't looked, issue with the alsa compliance test itself, possibly regarding frame counts of usb devices?

detail below. 

5 passed, 0 failed
Device Information
	Name: hw:CARD=H340
	Stream: CAPTURE
	Format: ['S16_LE']
	Channels range: [2, 2]
	Rate: [44100]
	Period_size range: [45, 131072]
	Buffer_size range: [90, 262144]
Test Params
	Set channels 2: pass
	Set format S16_LE: pass
	Set rate 44100: pass
Test Rates
	Set rate 44100: pass
Test All Pairs
	Set channels 2, format S16_LE, rate 44100: pass

3 passed, 2 failed
Device Information
	Name: hw:CARD=H340
	Stream: PLAYBACK
	Format: ['S16_LE']
	Channels range: [2, 2]
	Rate: [44100]
	Period_size range: [45, 131072]
	Buffer_size range: [90, 262144]
Test Params
	Set channels 2: pass
	Set format S16_LE: pass
	Set rate 44100: pass
Test Rates
	Set rate 44100: fail - Expected rate is 44100.000000, measure 44092.918362, difference 7.081638 > threshold 4.410000
Test All Pairs
	Set channels 2, format S16_LE, rate 44100: fail - Expected rate is 44100.000000, measure 44093.049192, difference 6.950808 > threshold 4.410000