[FFmpeg-devel] [PATCH v4 1/2] lavc: add HWACCEL_CAP_RESET_WITHOUT_UNINIT capacity for hwaccel

[Fei Wang <fei.w.wang-at-intel.com@ffmpeg.org>]

The capacity can avoid hwaccel being uninited when do the reset. It
provides the method for hwaccel if it still want to use the previous
initialized configuration after reset. And the configuration can be
updated in AVHWAccel.init() if needed.

For example, when use vaapi vp9 decode dynamic resolution clips, need
to avoid changing vaContext in avctx->internal->hwaccel_priv_data if
current frame resolution change and it reference a pervious frame with
different resolution. Otherwise reference frame's information bound
in vaContext will be lost, then corrupt current frame.

Signed-off-by: Fei Wang <fei.w.wang@intel.com>
---
 libavcodec/decode.c   | 10 ++++++----
 libavcodec/hwconfig.h |  7 +++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 6be2d3d6ed..cfada048e8 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -1109,7 +1109,7 @@ static int hwaccel_init(AVCodecContext *avctx,
         return AVERROR_PATCHWELCOME;
     }
 
-    if (hwaccel->priv_data_size) {
+    if (hwaccel->priv_data_size && !avctx->internal->hwaccel_priv_data) {
         avctx->internal->hwaccel_priv_data =
             av_mallocz(hwaccel->priv_data_size);
         if (!avctx->internal->hwaccel_priv_data)
@@ -1134,10 +1134,12 @@ static int hwaccel_init(AVCodecContext *avctx,
 
 static void hwaccel_uninit(AVCodecContext *avctx)
 {
-    if (avctx->hwaccel && avctx->hwaccel->uninit)
-        avctx->hwaccel->uninit(avctx);
+    if (avctx->hwaccel && !(avctx->hwaccel->caps_internal & HWACCEL_CAP_RESET_WITHOUT_UNINIT)) {
+        if (avctx->hwaccel->uninit)
+            avctx->hwaccel->uninit(avctx);
 
-    av_freep(&avctx->internal->hwaccel_priv_data);
+        av_freep(&avctx->internal->hwaccel_priv_data);
+    }
 
     avctx->hwaccel = NULL;
 
diff --git a/libavcodec/hwconfig.h b/libavcodec/hwconfig.h
index 721424912c..5fb4e06d5f 100644
--- a/libavcodec/hwconfig.h
+++ b/libavcodec/hwconfig.h
@@ -25,6 +25,13 @@
 
 #define HWACCEL_CAP_ASYNC_SAFE      (1 << 0)
 
+/**
+ * The hwaccel supports reset without calling back AVHWAccel.uninit()
+ * and realloc avctx->internal->hwaccel_priv_data.
+ *
+ * New configuration can set up through AVHWAccel.init().
+ */
+#define HWACCEL_CAP_RESET_WITHOUT_UNINIT     (1 << 1)
 
 typedef struct AVCodecHWConfigInternal {
     /**
-- 
2.25.1

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