Re: [PATCH] Optimization on QSV Flush

Bumping this as it fixes an issue we are having when decoding keyframes only

Michael Bodenhoff
Principal Software Engineer
www.milestonesys.com<http://www.milestonesys.com>
________________________________
From: Kumar, Pradeep via ffmpeg-devel <[email protected]>
Sent: Tuesday, 7 July 2026 07.29
To: [email protected] <[email protected]>
Cc: Kumar, Pradeep <[email protected]>
Subject: [FFmpeg-devel] [PATCH] Optimization on QSV Flush

Signed-off-by: Kumar, Pradeep <[email protected]>
---
 libavcodec/qsvdec.c | 72 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 2 deletions(-)

diff --git a/libavcodec/qsvdec.c b/libavcodec/qsvdec.c
index a85c1785cf..510cff2887 100644
--- a/libavcodec/qsvdec.c
+++ b/libavcodec/qsvdec.c
@@ -572,6 +572,34 @@ static void qsv_clear_unused_frames(QSVContext *q)
     }
 }

+
+static void qsv_clear_async(QSVContext *q)
+{
+    QSVAsyncFrame aframe;
+    QSVFrame *cur;
+    if (q->async_fifo) {
+        while (av_fifo_read(q->async_fifo, &aframe, 1) >= 0) {
+            if (aframe.frame && aframe.frame->queued > 0)
+                aframe.frame->queued -= 1;
+            av_freep(&aframe.sync);
+        }
+    }
+
+    cur = q->work_frames;
+    while (cur) {
+        cur->queued = 0;
+        if (cur->used && !cur->surface.Data.Locked) {
+            cur->used = 0;
+            av_frame_unref(cur->frame);
+        }
+        cur = cur->next;
+    }
+
+    q->zero_consume_run = 0;
+    q->reinit_flag = 0;
+}
+
+
 static int get_surface(AVCodecContext *avctx, QSVContext *q, mfxFrameSurface1 **surf)
 {
     QSVFrame *frame, **last;
@@ -1207,11 +1235,51 @@ static int qsv_decode_frame(AVCodecContext *avctx, AVFrame *frame,
 static void qsv_decode_flush(AVCodecContext *avctx)
 {
     QSVDecContext *s = avctx->priv_data;
+    mfxStatus sts;
+    mfxVideoParam param = { { { 0 } } };
+    int reset_succeeded = 0;

     qsv_clear_buffers(s);
+    qsv_clear_async(&s->qsv);
+
+    // Intel Media SDK compatibility: Try decoder reset first to avoid
+    // expensive full teardown/reinit cycle (15-20ms -> 2-3ms optimization)
+    if (s->qsv.session && s->qsv.initialized) {
+        av_log(avctx, AV_LOG_DEBUG,
+            "Attempting QSV decoder reset for fast flush\n");
+
+        sts = MFXVideoDECODE_GetVideoParam(s->qsv.session, &param);
+        if (sts == MFX_ERR_NONE) {
+            // Restore critical parameters for reset
+            param.AsyncDepth = s->qsv.async_depth;
+            param.IOPattern  = s->qsv.iopattern;
+            param.ExtParam   = s->qsv.ext_buffers;
+            param.NumExtParam = s->qsv.nb_ext_buffers;
+
+            sts = MFXVideoDECODE_Reset(s->qsv.session, &param);
+            if (sts >= 0) {
+                av_log(avctx, AV_LOG_DEBUG,
+                     "QSV decoder reset successful (fast path)\n");
+                s->qsv.frame_info = param.mfx.FrameInfo;
+                reset_succeeded = 1;
+            } else {
+                av_log(avctx, AV_LOG_WARNING,
+                    "MFXVideoDECODE_Reset failed (%d),"
+                    "forcing full reinit\n", sts);
+            }
+        } else {
+            av_log(avctx, AV_LOG_WARNING,
+                   "MFXVideoDECODE_GetVideoParam failed (%d),"
+                   "forcing full reinit\n", sts);
+        }
+    }

-    s->qsv.orig_pix_fmt = AV_PIX_FMT_NONE;
-    s->qsv.initialized = 0;
+    if (!reset_succeeded) {
+        // Fallback to full reinitialization
+        av_log(avctx, AV_LOG_DEBUG, "Using full QSV decoder reinitialization\n");
+        s->qsv.orig_pix_fmt = AV_PIX_FMT_NONE;
+        s->qsv.initialized = 0;
+    }
 }

 #define OFFSET(x) offsetof(QSVDecContext, x)
--
2.34.1

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