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