At Sat, 01 May 2010 11:36:03 -0400, Ben Collins wrote:
I'm writing a driver for a card that only has hardware support for G.723-24 ADPCM format. I am working around the lack of support in alsa at the moment for this format, but wanted to take a crack at implementing it properly.
G.723-24 is a 3-bit signed sample at a fixed 8khz mono sample rate (24000 bit rate). Basically means you need to take in at least 3 bytes (8 samples) minimum for processing the standard packed version.
I don't have hardware that supports it, but since I was in the code, I added a G723_24_1B format for producing 1 sample per byte (3 lower bits are actual sample), but for my use I am producing the standard packed stream.
Only question I had is that since this is signed, should I expect or want the _1B version to be a 1 byte sign extended version of the 3-bit sample, or just expect the lower 3 bits of the byte to be the g723-24 sample? Looking at other unpacked examples, I assume the latter rather than the former.
I suppose both are non-linear formats, so you shouldn't give signed/unsigned flags for them. Otherwise snd_pcm_format_linear() will return 1.
Other than that, addition of these new formats look good to me.
thanks,
Takashi
diff --git a/include/sound/asound.h b/include/sound/asound.h index 1f57bb9..16fc633 100644 --- a/include/sound/asound.h +++ b/include/sound/asound.h @@ -212,7 +212,9 @@ typedef int __bitwise snd_pcm_format_t; #define SNDRV_PCM_FORMAT_S18_3BE ((__force snd_pcm_format_t) 41) /* in three bytes */ #define SNDRV_PCM_FORMAT_U18_3LE ((__force snd_pcm_format_t) 42) /* in three bytes */ #define SNDRV_PCM_FORMAT_U18_3BE ((__force snd_pcm_format_t) 43) /* in three bytes */ -#define SNDRV_PCM_FORMAT_LAST SNDRV_PCM_FORMAT_U18_3BE +#define SNDRV_PCM_FORMAT_G723_24 ((__force snd_pcm_format_t) 44) /* 8 samples in 3 bytes */ +#define SNDRV_PCM_FORMAT_G723_24_1B ((__force snd_pcm_format_t) 45) /* 1 sample in 1 byte */ +#define SNDRV_PCM_FORMAT_LAST SNDRV_PCM_FORMAT_G723_24_1B
#ifdef SNDRV_LITTLE_ENDIAN #define SNDRV_PCM_FORMAT_S16 SNDRV_PCM_FORMAT_S16_LE diff --git a/include/sound/pcm.h b/include/sound/pcm.h index de6d981..031e2cd 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -173,6 +173,8 @@ struct snd_pcm_ops { #define SNDRV_PCM_FMTBIT_U18_3LE (1ULL << SNDRV_PCM_FORMAT_U18_3LE) #define SNDRV_PCM_FMTBIT_S18_3BE (1ULL << SNDRV_PCM_FORMAT_S18_3BE) #define SNDRV_PCM_FMTBIT_U18_3BE (1ULL << SNDRV_PCM_FORMAT_U18_3BE) +#define SNDRV_PCM_FMTBIT_G723_24 (1ULL << SNDRV_PCM_FORMAT_G723_24) +#define SNDRV_PCM_FMTBIT_G723_24_1B (1ULL << SNDRV_PCM_FORMAT_G723_24_1B)
#ifdef SNDRV_LITTLE_ENDIAN #define SNDRV_PCM_FMTBIT_S16 SNDRV_PCM_FMTBIT_S16_LE diff --git a/sound/core/pcm_misc.c b/sound/core/pcm_misc.c index ea2bf82..c7f8da4 100644 --- a/sound/core/pcm_misc.c +++ b/sound/core/pcm_misc.c @@ -128,6 +128,10 @@ static struct pcm_format_data pcm_formats[SNDRV_PCM_FORMAT_LAST+1] = { .width = 4, .phys = 4, .le = -1, .signd = -1, .silence = {}, },
- [SNDRV_PCM_FORMAT_G723_24] = {
.width = 3, .phys = 3, .le = -1, .signd = 1,.silence = {},- }, /* FIXME: the following three formats are not defined properly yet */ [SNDRV_PCM_FORMAT_MPEG] = { .le = -1, .signd = -1,
@@ -186,6 +190,10 @@ static struct pcm_format_data pcm_formats[SNDRV_PCM_FORMAT_LAST+1] = { .width = 18, .phys = 24, .le = 0, .signd = 0, .silence = { 0x02, 0x00, 0x00 }, },
- [SNDRV_PCM_FORMAT_G723_24_1B] = {
.width = 3, .phys = 8, .le = -1, .signd = 1,.silence = {},- },
};
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