Commit 71373fdd authored Nov 10, 2013 by Anssi Hannula Committed by Takashi Iwai Nov 11, 2013

ALSA: usb: Fix wrong mapping of RLC and RRC channels



According to USB Audio spec v2 bits 25 and 26 of bmChannelConfig are
"Back Left of Center - BLC" and "Back Right of Center - BRC",
respectively.

They are currently assigned to ALSA channels BLC/BRC. However, the ALSA
BLC/BRC are actually the rather nonsensical "bottom left center" and
"bottom right center", so the channels will be assigned wrongly. The
comments in the USB code are also similarly wrong, so this is not
readily apparent without looking at the actual specification.

Fix the channel mapping by mapping bits 25 and 26 to RLC (Rear Left
Center) and RRC (Rear Right Center), respectively, instead.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 94908a39

sound/usb/stream.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -273,8 +273,8 @@ static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
		SNDRV_CHMAP_TSL, /* top side left */
		SNDRV_CHMAP_TSR, /* top side right */
		SNDRV_CHMAP_BC, /* bottom center */
		SNDRV_CHMAP_BLC, /* bottom left center */
		SNDRV_CHMAP_BRC, /* bottom right center */
		SNDRV_CHMAP_RLC, /* back left of center */
		SNDRV_CHMAP_RRC, /* back right of center */
		0 /* terminator */
		};
		struct snd_pcm_chmap_elem *chmap;

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