Hardware pixel formats do not tell you anything about their actual
contents, but should still score higher than formats with completely
unknown properties, which in turn should score higher than invalid
formats.
Do not return an AVERROR code as a score.
Fixes a hang in libavfilter where format negotiation gets stuck in a
loop because AV_PIX_FMT_NONE scores more highly than all other
possibilities.
---
The hang in libavfilter happens when trying to choose a pixfmt for output from
a list of software formats when a hardware format is the input (the hwdownload
filter does this). The matching begins with AV_PIX_FMT_NONE as an invalid
value and compares against each possibility in turn, but unfortunately it
scores -1 when considered as a conversion from an opaque hardware format,
higher than the AVERROR(EINVAL) (== -22 on Linux) scored for all of the real
formats. Hence the format selection code chooses AV_PIX_FMT_NONE and thinks it
is making forward progress, but actually hasn't and therefore gets stuck in an
infinite loop.
libavutil/pixdesc.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/libavutil/pixdesc.c b/libavutil/pixdesc.c
index 46a7eff06d..35b63f43c6 100644
--- a/libavutil/pixdesc.c
+++ b/libavutil/pixdesc.c
@@ -2512,7 +2512,11 @@ static int get_pix_fmt_score(enum AVPixelFormat
dst_pix_fmt,
int score = INT_MAX - 1;
if (dst_pix_fmt >= AV_PIX_FMT_NB || dst_pix_fmt <= AV_PIX_FMT_NONE)
- return ~0;
+ return -2;
+
+ if ((src_desc->flags & AV_PIX_FMT_FLAG_HWACCEL) ||
+ (dst_desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
+ return 0;
/* compute loss */
*lossp = loss = 0;
@@ -2521,9 +2525,9 @@ static int get_pix_fmt_score(enum AVPixelFormat
dst_pix_fmt,
return INT_MAX;
if ((ret = get_pix_fmt_depth(&src_min_depth, &src_max_depth, src_pix_fmt))
< 0)
- return ret;
+ return -1;
if ((ret = get_pix_fmt_depth(&dst_min_depth, &dst_max_depth, dst_pix_fmt))
< 0)
- return ret;
+ return -1;
src_color = get_color_type(src_desc);
dst_color = get_color_type(dst_desc);
--
2.11.0
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