avcodec/v4l2_m2m: handle v4l2 end of stream event

When flushing the capture buffers, the driver may send a V4L2_EVENT_EOS
to notify that draining is completed. Currently, v4l2_m2m does not
subscribe to this event, which can cause some devices (i.e. imx8qm) to
hang at the end of encoding/decoding. Support for handling the event is
added in this commit.

Some devices may not signal V4L2_EVENT_EOS. This is logged as a warning
message during initialization and not treated as a fatal error.
Signed-off-by: Ming Qian <ming.qian@nxp.com>
Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>

libavcodec/v4l2_context.c

@@ -154,6 +154,7 @@ static inline void v4l2_save_to_context(V4L2Context* ctx, struct v4l2_format_upd
 }
 
 /**
+ * handle resolution change event and end of stream event
  * returns 1 if reinit was successful, negative if it failed
  * returns 0 if reinit was not executed
  */
@@ -171,6 +172,11 @@ static int v4l2_handle_event(V4L2Context *ctx)
         return 0;
     }
 
+    if (evt.type == V4L2_EVENT_EOS) {
+        ctx->done = 1;
+        return 0;
+    }
+
     if (evt.type != V4L2_EVENT_SOURCE_CHANGE)
         return 0;
 

libavcodec/v4l2_m2m_dec.c

@@ -123,6 +123,13 @@ static int v4l2_prepare_decoder(V4L2m2mContext *s)
         }
     }
 
+    memset(&sub, 0, sizeof(sub));
+    sub.type = V4L2_EVENT_EOS;
+    ret = ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub);
+    if (ret < 0)
+        av_log(s->avctx, AV_LOG_WARNING,
+               "the v4l2 driver does not support end of stream VIDIOC_SUBSCRIBE_EVENT\n");
+
     return 0;
 }
 

libavcodec/v4l2_m2m_enc.c

@@ -155,6 +155,17 @@ static int v4l2_check_b_frame_support(V4L2m2mContext *s)
     return AVERROR_PATCHWELCOME;
 }
 
+static inline void v4l2_subscribe_eos_event(V4L2m2mContext *s)
+{
+    struct v4l2_event_subscription sub;
+
+    memset(&sub, 0, sizeof(sub));
+    sub.type = V4L2_EVENT_EOS;
+    if (ioctl(s->fd, VIDIOC_SUBSCRIBE_EVENT, &sub) < 0)
+        av_log(s->avctx, AV_LOG_WARNING,
+               "the v4l2 driver does not support end of stream VIDIOC_SUBSCRIBE_EVENT\n");
+}
+
 static int v4l2_prepare_encoder(V4L2m2mContext *s)
 {
     AVCodecContext *avctx = s->avctx;
@@ -164,6 +175,8 @@ static int v4l2_prepare_encoder(V4L2m2mContext *s)
     /**
      * requirements
      */
+    v4l2_subscribe_eos_event(s);
+
     ret = v4l2_check_b_frame_support(s);
     if (ret)
         return ret;