thread assertion if avcodec_get_hw_frames_parameters fails

[François Cartegnie]

Summary of the bug:

Using libavcodec for decoding VP9 leads to assertion due to missing priv_data cleanup on failed VAAPI acceleration.

release/7.0 e7d2238ad751e4ce4ebc5118af750fd5cc0c5055

libva info: VA-API version 1.20.0
libva info: Trying to open /usr/lib64/dri/iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_20
libva info: va_openDriver() returns 0
[vp9 @ 0x619000022180] No support for codec vp9 profile 0.
[0000604000066ad0] vaapi generic error: avcodec_get_hw_frames_parameters failed: -38
Assertion p_dst->hwaccel_threadsafe || (!dst->hwaccel && !dst->internal->hwaccel_priv_data) failed at libavcodec/pthread_frame.c:348

Fix attempt

diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c
index fd356bd190..a13bb9e996 100644
--- a/libavcodec/pthread_frame.c
+++ b/libavcodec/pthread_frame.c
@@ -344,6 +344,10 @@ FF_ENABLE_DEPRECATION_WARNINGS
                 return err;
         }
 
+       // hwaccel could have failed init due to some params
+       if(!dst->hwaccel && dst->internal->hwaccel_priv_data)
+           ff_hwaccel_uninit(dst);
+
         // reset dst hwaccel state if needed
         av_assert0(p_dst->hwaccel_threadsafe ||
                    (!dst->hwaccel && !dst->internal->hwaccel_priv_data));

How to reproduce:

Sample reference

4d8e399e9ecf06363840f3a7880e0e2937d527438bcf87bb3c250e5f4ac71c7e Agent 327 - Operation Barbershop.web