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chmap_sel: add a mechanism for preferred conversions

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And use it for the mono case. This is slightly more formal and will make
it easier to add more such cases.
This commit is contained in:
wm4 2015-06-27 12:09:30 +02:00
parent e0a7e094bc
commit 0969502316
1 changed files with 39 additions and 9 deletions
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48
audio/chmap_sel.c
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@ -58,6 +58,29 @@ static bool replace_speakers(struct mp_chmap *map, struct mp_chmap list[2])
return false;
}
// These go strictly from the first to the second entry and always use the
// full layout (possibly reordered and/or padding channels added).
static const struct mp_chmap preferred_remix[][2] = {
// mono can be perfectly played as stereo
{ MP_CHMAP_INIT_MONO, MP_CHMAP_INIT_STEREO },
};
// Conversion from src to dst is explicitly encouraged and should be preferred
// over "mathematical" upmixes or downmixes (which minimize lost channels).
static bool test_preferred_remix(const struct mp_chmap *src,
const struct mp_chmap *dst)
{
struct mp_chmap src_p = *src, dst_p = *dst;
mp_chmap_remove_na(&src_p);
mp_chmap_remove_na(&dst_p);
for (int n = 0; n < MP_ARRAY_SIZE(preferred_remix); n++) {
if (mp_chmap_equals_reordered(&src_p, &preferred_remix[n][0]) &&
mp_chmap_equals_reordered(&dst_p, &preferred_remix[n][1]))
return true;
}
return false;
}
// Allow all channel layouts that can be expressed with mp_chmap.
// (By default, all layouts are rejected.)
void mp_chmap_sel_add_any(struct mp_chmap_sel *s)
@ -218,6 +241,14 @@ static int mp_chmap_diffn_r(const struct mp_chmap *a, const struct mp_chmap *b)
mindiff = d;
}
// Special-case: we consider stereo a replacement for mono. (This is not
// true in the other direction. Also, fl-fr is generally not a replacement
// for fc. Thus it's not part of the speaker replacement list.)
struct mp_chmap mono = MP_CHMAP_INIT_MONO;
struct mp_chmap stereo = MP_CHMAP_INIT_STEREO;
if (mp_chmap_equals(&mono, b) && mp_chmap_equals(&stereo, a))
mindiff = 0;
return mindiff;
}
@ -238,6 +269,14 @@ static bool mp_chmap_is_better(struct mp_chmap *req, struct mp_chmap *old,
if (mp_chmap_equals(req, new))
return true;
// If there's no exact match, strictly do a preferred conversion.
bool old_pref = test_preferred_remix(req, old);
bool new_pref = test_preferred_remix(req, new);
if (old_pref && !new_pref)
return false;
if (!old_pref && new_pref)
return true;
int old_lost_r = mp_chmap_diffn_r(req, old); // num. channels only in req
int new_lost_r = mp_chmap_diffn_r(req, new);
@ -272,15 +311,6 @@ static bool mp_chmap_is_better(struct mp_chmap *req, struct mp_chmap *old,
// Determine which channel map to fallback to given a source channel map.
bool mp_chmap_sel_fallback(const struct mp_chmap_sel *s, struct mp_chmap *map)
{
// special case: if possible always fallback mono to stereo (instead of
// looking for a multichannel upmix)
struct mp_chmap mono = MP_CHMAP_INIT_MONO;
struct mp_chmap stereo = MP_CHMAP_INIT_STEREO;
if (mp_chmap_equals(&mono, map) && test_layout(s, &stereo)) {
*map = stereo;
return true;
}
struct mp_chmap best = {0};
for (int n = 0; n < s->num_chmaps; n++) {