[FFmpeg-devel] [PATCH 1/2] lavu/hwcontext_vaapi: dump more decoding error details.

[Mark Thompson]

On 23/05/18 11:29, Jun Zhao wrote:
> dump more decoding error details when sync surface fail.
> 
> Signed-off-by: Jun Zhao <mypopydev at gmail.com>
> ---
>  libavutil/hwcontext_vaapi.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/libavutil/hwcontext_vaapi.c b/libavutil/hwcontext_vaapi.c
> index e55bb8d..5bdb02f 100644
> --- a/libavutil/hwcontext_vaapi.c
> +++ b/libavutil/hwcontext_vaapi.c
> @@ -742,6 +742,23 @@ static int vaapi_map_frame(AVHWFramesContext *hwfc,
>          av_log(hwfc, AV_LOG_ERROR, "Failed to sync surface "
>                 "%#x: %d (%s).\n", surface_id, vas, vaErrorStr(vas));
>          err = AVERROR(EIO);
> +        /* query decode detail error */
> +        if (vas == VA_STATUS_ERROR_DECODING_ERROR) {
> +            VASurfaceDecodeMBErrors *dec_err = NULL;
> +            int i;
> +            vas = vaQuerySurfaceError(hwctx->display, surface_id, VA_STATUS_ERROR_DECODING_ERROR,
> +                                      (void **)&dec_err);
> +            if (VA_STATUS_SUCCESS == vas) {
> +                if (NULL != dec_err) {

Why this check?

> +                    for (i = 0; dec_err[i].status != -1; i++) {

How many items can be in this list?  We probably don't want to print more than one in the error log if this can happen on every frame in a broken stream.

> +                          av_log(hwfc, AV_LOG_ERROR, "Decoding deatils error, "

"Decoding error details:" maybe?

> +                                 "type: %d, start mb: %d, end md: %d, num mbs: %d.\n",
> +                                 dec_err[i].decode_error_type, dec_err[i].start_mb,
> +                                 dec_err[i].end_mb, dec_err[i].num_mb);
> +                    }
> +                }
> +            }
> +        }
>          goto fail;
>      }
>  
> 

What is the lifetime of the returned pointer here?  This can certainly be called on any thread asynchronously.

It's a bit nasty to have this in the generic code rather than the decoder: very few actual uses are going to call SyncSurface directly on a decoder output - rather they will pass it to some other component (another VAAPI one, or export).  Could we instead put this inside the decoder, enabled by some debug option?  (Some sort of "catch decoder errors earlier at a cost of (possibly greatly) decreased performance" flag.)

- Mark