On 2019-08-03 00:09, Timo Rothenpieler wrote:
On 02.08.2019 11:18, Stefan Schoenefeld wrote:
Hi all,
Recently we encountered an issue when decoding a h.263 file:
FFmpeg will freeze when decoding h.263 video with NVDEC. Turns out
this is not directly related to NVDEC but is a problem that shows with
several other HW decoders like VDPAU, though the exact kind of error
is different (either error messages or freezing[1]). The root cause is
that ff_thread_finish_setup() is called twice per frame from
ff_h263_decode_frame(). This is not supported by
ff_thread_finish_setup() and specifically checked for and warned
against in the functions code. The issue is also specific to hw
accelerated decoding only as the second call to
ff_thread_finish_setup() is only issued when hw acceleration is on.
The fix is simple: add a check that the first call is only send when
hw acceleration is off, and the second call only when hw acceleration
is on (see attached patch). This works fine as far as I was able to
test with vdpau and nvdec/nvcuvid hw decoding. The patch also adds
NVDEC to the hw config list if available.
I also noticed a secondary issue when browsing through the code which
is that, according to documentation, ff_thread_finish_setup() should
only be called if the codec implements update_thread_context(), which
h263dec does not. The patch does not address this and I'm not sure any
action needs to be taken here at all.
Thanks,
Stefan
[1] This is depending on whether or not the hw decoder sets the
HWACCEL_CAPS_ASYNC_SAFE flag
From 0620ee777a8ba98145bb4781e30a77687c97dbf8 Mon Sep 17 00:00:00
2001
From: Stefan Schoenefeld <sschoenef...@nvidia.com>
Date: Fri, 2 Aug 2019 10:52:22 +0200
Subject: [PATCH] Fixing HW accelerated decoders hanging or throwing
error
messages in h263dec
---
libavcodec/h263dec.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
index 6f001f6..8ee844e 100644
--- a/libavcodec/h263dec.c
+++ b/libavcodec/h263dec.c
@@ -614,7 +614,7 @@ retry:
if ((ret = ff_mpv_frame_start(s, avctx)) < 0)
return ret;
- if (!s->divx_packed)
+ if (!s->divx_packed && !avctx->hwaccel)
ff_thread_finish_setup(avctx);
This seems correct to me, but I'd like another pair of eyes to look
over it.
Seems fine to me as well.
if (avctx->hwaccel) {
@@ -747,6 +747,9 @@ const AVCodecHWConfigInternal
*ff_h263_hw_config_list[] = {
#if CONFIG_H263_VAAPI_HWACCEL
HWACCEL_VAAPI(h263),
#endif
+#if CONFIG_MPEG4_NVDEC_HWACCEL
+ HWACCEL_NVDEC(mpeg4),
+#endif
Probably cleaner to split this into its own patch, but otherwise OK.
#if CONFIG_MPEG4_VDPAU_HWACCEL
HWACCEL_VDPAU(mpeg4),
#endif
Thanks for fixing this. I was always confused about whether h.263 was
really supported by
the hardware or not. Can you provide a link to a reference sample that
fails without this
change and succeeds with it?
--phil
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