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af_lavrresample: fudge some channel layout conversion 

Prevents channels from being dropped, e.g. when going 7.1 -> 7.1(wide)
and similar cases. The reasoning here is that channel layouts over HDMI
don't work anyway, and not dropping a channel and playing it on a
slightly "wrong" (but expected) speaker is preferable to playing silence
on these speakers.

Do this to remove issues with ao_coreaudio. Frankly I'm not sure whether
our mapping (between CA and mpv/FFmpeg speakers) is correct, but on the
other hand due to the reasons stated above it's not all that meaningful.
This commit is contained in:
wm4 2016-01-18 16:31:26 +01:00
parent 0ed170ec0b
commit 418c98dec7
1 changed files with 33 additions and 0 deletions
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33
audio/filter/af_lavrresample.c
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@ -179,6 +179,37 @@ bool af_lavrresample_test_conversion(int src_format, int dst_format)
check_output_conversion(dst_format) != AV_SAMPLE_FMT_NONE;
}
static struct mp_chmap fudge_pairs[][2] = {
{MP_CHMAP2(FLC, FRC), MP_CHMAP2(SL, SR)},
{MP_CHMAP2(SL, SR), MP_CHMAP2(FLC, FRC)},
{MP_CHMAP2(SDL, SDR), MP_CHMAP2(SL, SR)},
{MP_CHMAP2(SL, SR), MP_CHMAP2(SDL, SDR)},
};
// Modify out_layout and return the new value. The intention is reducing the
// loss libswresample's rematrixing will cause by exchanging similar, but
// strictly speaking incompatible channel pairs. For example, 7.1 should be
// changed to 7.1(wide) without dropping the SL/SR channels. (We still leave
// it to libswresample to create the remix matrix.)
static uint64_t fudge_layout_conversion(struct af_instance *af,
uint64_t in, uint64_t out)
{
for (int n = 0; n < MP_ARRAY_SIZE(fudge_pairs); n++) {
uint64_t a = mp_chmap_to_lavc(&fudge_pairs[n][0]);
uint64_t b = mp_chmap_to_lavc(&fudge_pairs[n][1]);
if ((in & a) == a && (in & b) == 0 &&
(out & a) == 0 && (out & b) == b)
{
out = (out & ~b) | a;
MP_VERBOSE(af, "Fudge: %s -> %s\n",
mp_chmap_to_str(&fudge_pairs[n][0]),
mp_chmap_to_str(&fudge_pairs[n][1]));
}
}
return out;
}
// mp_chmap_get_reorder() performs:
// to->speaker[n] = from->speaker[src[n]]
// but libavresample does:
@ -297,6 +328,8 @@ static int configure_lavrr(struct af_instance *af, struct mp_audio *in,
if (map_out.num > out_lavc.num)
mp_audio_set_channels(&s->pool_fmt, &map_out);
out_ch_layout = fudge_layout_conversion(af, in_ch_layout, out_ch_layout);
// Real conversion; output is input to avrctx_out.
av_opt_set_int(s->avrctx, "in_channel_layout", in_ch_layout, 0);
av_opt_set_int(s->avrctx, "out_channel_layout", out_ch_layout, 0);