On 4/7/2024 6:53 PM, Andreas Rheinhardt wrote:
James Almer:
On 4/7/2024 5:39 PM, Andreas Rheinhardt wrote:
It is perfectly legal for users to use a custom layout
that is equivalent to a supported native one.
Is that really the case? FFCodec.p.ch_layouts[] has a list of native
ones, and the generic encode.c code will reject anything not in it.
This is not true. It allows everything that is equivalent (in the
av_channel_layout_compare() sense) to one of the channel layouts in
AVCodec.ch_layouts. This means that if ch_layout.u.map[i].id is strictly
ascending for 0 <= i <nb_channels and < 64, then it is equivalent to the
native channel layout with the same nb_channels whose mask is the
bitwise or of all (1ULL << ch_layout.u.map[i].id).
Right, misread av_channel_layout_compare() as rejecting layouts that
were not the same order.
I guess the encode.c check could be improved with
av_channel_layout_retype().
ch_layout is not supposed to be set by lavc for encoders.
I didn't mean to set the layout for encoders, i meant it as a way for
encode.c to compare input layouts with encoder-supported native layouts,
because of my misunderstanding of how av_channel_layout_compare() behaved.
In this case the union in AVChannelLayout is not an uint64_t mask,
but a pointer to a custom map.
Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com>
---
libavcodec/ac3enc.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index 7a6bcf7900..dc197c1517 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -2192,18 +2192,14 @@ av_cold int ff_ac3_encode_close(AVCodecContext
*avctx)
static av_cold int set_channel_info(AVCodecContext *avctx)
{
AC3EncodeContext *s = avctx->priv_data;
+ uint64_t mask = av_channel_layout_subset(&avctx->ch_layout,
~(uint64_t)0);
Might as well use UINT64_MAX.
This is a bitfield, so I intentionally used a bit-operation.
Then ~UINT64_C(0).
int channels = avctx->ch_layout.nb_channels;
- uint64_t mask = avctx->ch_layout.u.mask;
if (channels < 1 || channels > AC3_MAX_CHANNELS)
return AVERROR(EINVAL);
if (mask > 0x7FF)
return AVERROR(EINVAL);
- if (!mask)
- av_channel_layout_default(&avctx->ch_layout, channels);
- mask = avctx->ch_layout.u.mask;
-
s->lfe_on = !!(mask & AV_CH_LOW_FREQUENCY);
s->channels = channels;
s->fbw_channels = channels - s->lfe_on;
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