On Tue, 11 Dec 2007, Timur Tabi wrote:
I'm confused about the entries for unsigned 24-bit sound in the pcm_formats[] array:
[SNDRV_PCM_FORMAT_U24_BE] = { .width = 24, .phys = 32, .le = 0, .signd = 0, .silence = { 0x80, 0x00, 0x00 }, },
and
[SNDRV_PCM_FORMAT_U24_3BE] = { .width = 24, .phys = 24, .le = 0, .signd = 0, .silence = { 0x80, 0x00, 0x00 }, },
SNDRV_PCM_FORMAT_U24_BE means a 24-bit sample packed into a 32-bit word. So I presume that if the 24-bit sample is:
0x123456
then when that sample is written to memory, it looks like this:
X X + 1 X + 2 X + 3 0x00 0x12 0x34 0x56
(where X is some address in memory).
If that's so, shouldn't the entry for SNDRV_PCM_FORMAT_U24_BE look like this:
[SNDRV_PCM_FORMAT_U24_BE] = { .width = 24, .phys = 32, .le = 0, .signd = 0, .silence = { 0x00, 0x80, 0x00, 0x00 }, }, ^^^^^^
Good catch. It looks like a bug and your proposal seems to be correct.
Jaroslav
----- Jaroslav Kysela perex@perex.cz Linux Kernel Sound Maintainer ALSA Project