[alsa-devel] [RFC] Channel mapping API (take 2)

[Raymond Yau]

2012-9-4 下午11:47 於 "Takashi Iwai" <tiwai at suse.de> 寫道：
>
> Hi,
>
> my proposal for channel mapping API seems accepted fairly well through
> discussions at Plumbers, so I continued to work on it and uploaded the
> updated version.
>
> The kernel part is found in sound-unstable tree topic/tlv-chmap branch
>   git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-unstable.git
>
> and the alsa-lib part is found in github tree topic/chmap branch
>   git://git.github.com/tiwai/alsa-lib.git
>
> The updated parts are:
>
> - SNDRV_CHMAP_NA was newly added, indicating the channel is not
>   available or silent.
>
> - The channel position value is masked in lower 16bit.
>   The upper bits are used for more channel attributes as bit flags.
>
>   #define SNDRV_CHMAP_POSITION_MASK     0xffff
>
>   The phase inverted channel has this bit:
>   #define SNDRV_CHMAP_PHASE_INVERSE     (0x01 << 16)
>
>   And the driver-specific non-standard channel position has this:
>   #define SNDRV_CHMAP_DRIVER_SPEC       (0x02 << 16)
>
> - The alsa-lib API functions use snd_pcm_chmap_query_t and
>   snd_pcm_chmap_t instead of ambiguous integer arrays.
>
> ================================================================
> /** the channel map header */
> typedef struct snd_pcm_chmap {
>         unsigned int channels;
>         unsigned int pos[0];
> } snd_pcm_chmap_t;
>
> /** the header of array items returned from snd_pcm_query_chmaps() */
> typedef struct snd_pcm_chmap_query {
>         enum snd_pcm_chmap_type type;
>         snd_pcm_chmap_t map;
> } snd_pcm_chmap_query_t;
>
>
> snd_pcm_chmap_query_t **snd_pcm_query_chmaps(snd_pcm_t *pcm);
> void snd_pcm_free_chmaps(snd_pcm_chmap_query_t **maps);
> snd_pcm_chmap_t *snd_pcm_get_chmap(snd_pcm_t *pcm);
> int snd_pcm_set_chmap(snd_pcm_t *pcm, const snd_pcm_chmap_t *map);
> ================================================================
>
> The rest aren't so much changed.  Only slight bug fixes.
>
> A big remaining question is whether the current kernel-side
> implementation is OK.  We may add some PCM ops pointer instead of the
> current style using the direct control tlv/read/write override.
> But the kernel-side API can be changed even later, so I don't worry
> about it so much for now, as long as we can keep the ABI definition.
>
>
some hda codec support AC_WCAP_LR_SWAP (e.g. the "Swap Center/LFE" switch)

git.kernel.org/?p=linux/kernel/git/tiwai/sound.git;a=commit;h=0fb87bb474f978446786263deff6263284e6e011

does your implementation have two channel maps for surround 5.1 for these
idt codecs?

how about the channal map of those internal subwoofer of notebook and those
external subwoofer (e.g. sonicmaster subwoofer )  alc663 using asus-mode4

https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/871808