While outwardly bizarre, this change makes the behaviour consistent
with other VAAPI encoders which sync to the encode /input/ picture in
order to wait for /output/ from the encoder.  It is not harmful on
i965 (because synchronisation already happens in vaRenderPicture(),
so it has no effect there), and it allows the encoder to work on
mesa/gallium which assumes this behaviour.
---

Following this change, encode works on AMD VCE using current gallium/mesa in 
hardware-only transcode cases with suitable options.

That is, things like:

./avconv -y -vaapi_device /dev/dri/renderD129 -hwaccel vaapi 
-hwaccel_output_format vaapi -i in.mp4 -an -c:v h264_vaapi -qp 20 -bf 0 out.mp4

(On my testing card B-frames are not supported and that capability is not 
reported, so you have to set it explicitly.)

Using a software decoder and hwupload with something like:

./avconv -y -vaapi_device /dev/dri/renderD129 -i in.mp4 -vf 
'format=nv12,hwupload' -an -c:v h264_vaapi -qp 20 -bf 0 out.mp4

doesn't currently work because the general case of vaSyncSurface() was broken 
recently by 
<https://cgit.freedesktop.org/mesa/mesa/commit/?id=c59628d11b134fc016388a170880f7646e100d6f>
 (segfaults).  Some versions before that change do work.

I poked the mesa-dev ML about it but haven't heard back; I'll pursue this 
further soon.  More interesting cases (multiple encodes, say) might variably 
work, but I think this vaSyncSurface() problem needs to be cleared up before 
doing anything further.

I've also made some updates to the wiki page 
<https://wiki.libav.org/Hardware/vaapi> to reflect current status.

Thanks,

- Mark


 libavcodec/vaapi_encode.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
index 7ec5340..dc6cdfe 100644
--- a/libavcodec/vaapi_encode.c
+++ b/libavcodec/vaapi_encode.c
@@ -109,10 +109,10 @@ static int vaapi_encode_wait(AVCodecContext *avctx,
     }

     av_log(avctx, AV_LOG_DEBUG, "Sync to pic %"PRId64"/%"PRId64" "
-           "(recon surface %#x).\n", pic->display_order,
-           pic->encode_order, pic->recon_surface);
+           "(input surface %#x).\n", pic->display_order,
+           pic->encode_order, pic->input_surface);

-    vas = vaSyncSurface(ctx->hwctx->display, pic->recon_surface);
+    vas = vaSyncSurface(ctx->hwctx->display, pic->input_surface);
     if (vas != VA_STATUS_SUCCESS) {
         av_log(avctx, AV_LOG_ERROR, "Failed to sync to picture completion: "
                "%d (%s).\n", vas, vaErrorStr(vas));
-- 
2.9.3

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