v4l2: Handle corrupted buffer with empty payload

This allow skipping buffer flagged with ERROR that has no payload.
This is typical behaviour when a recovererable error occured during
capture in the driver, but that no valid data was ever written into that
buffer. This patch also translate V4L2_BUF_FLAG_ERROR into
GST_BUFFER_FLAG_CORRUPTED. Hence decoding error produce
by decoder due to missing frames will now be correctly marked. Finally,
this fixes a buffer leak when EOS is reached.

https://bugzilla.gnome.org/show_bug.cgi?id=740040

sys/v4l2/gstv4l2bufferpool.c

@@ -1129,6 +1129,9 @@ gst_v4l2_buffer_pool_dqbuf (GstV4l2BufferPool * pool, GstBuffer ** buffer)
       GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_DELTA_UNIT);
   }
 
+  if (group->buffer.flags & V4L2_BUF_FLAG_ERROR)
+    GST_BUFFER_FLAG_SET (outbuf, GST_BUFFER_FLAG_CORRUPTED);
+
   GST_BUFFER_TIMESTAMP (outbuf) = timestamp;
 
   *buffer = outbuf;
@@ -1595,8 +1598,12 @@ gst_v4l2_buffer_pool_process (GstV4l2BufferPool * pool, GstBuffer ** buf)
           GstBuffer *tmp;
 
           if ((*buf)->pool == bpool) {
-            if (gst_buffer_get_size (*buf) == 0)
+            if (gst_buffer_get_size (*buf) == 0) {
+              if (GST_BUFFER_FLAG_IS_SET (*buf, GST_BUFFER_FLAG_CORRUPTED))
+                goto buffer_corrupted;
+              else
                 goto eos;
+            }
 
             /* start copying buffers when we are running low on buffers */
             if (g_atomic_int_get (&pool->num_queued) < pool->copy_threshold) {
@@ -1632,6 +1639,10 @@ gst_v4l2_buffer_pool_process (GstV4l2BufferPool * pool, GstBuffer ** buf)
           /* An empty buffer on capture indicates the end of stream */
           if (gst_buffer_get_size (tmp) == 0) {
             gst_v4l2_buffer_pool_release_buffer (bpool, tmp);
+
+            if (GST_BUFFER_FLAG_IS_SET (*buf, GST_BUFFER_FLAG_CORRUPTED))
+              goto buffer_corrupted;
+            else
               goto eos;
           }
 
@@ -1787,10 +1798,19 @@ copy_failed:
     GST_ERROR_OBJECT (pool, "failed to copy buffer");
     return ret;
   }
+buffer_corrupted:
+  {
+    GST_WARNING_OBJECT (pool, "Dropping corrupted buffer without payload");
+    gst_buffer_unref (*buf);
+    *buf = NULL;
+    return GST_V4L2_FLOW_CORRUPTED_BUFFER;
+  }
 eos:
   {
     GST_DEBUG_OBJECT (pool, "end of stream reached");
-    return GST_FLOW_EOS;
+    gst_buffer_unref (*buf);
+    *buf = NULL;
+    return GST_V4L2_FLOW_LAST_BUFFER;
   }
 acquire_failed:
   {

sys/v4l2/gstv4l2bufferpool.h

@@ -44,6 +44,16 @@ G_BEGIN_DECLS
 #define GST_V4L2_BUFFER_POOL(obj)      (G_TYPE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_V4L2_BUFFER_POOL, GstV4l2BufferPool))
 #define GST_V4L2_BUFFER_POOL_CAST(obj) ((GstV4l2BufferPool*)(obj))
 
+/* This flow return is used to indicated that the last buffer of a
+ * drain or a resoltuion change has been found. This should normally
+ * only occure for mem-2-mem devices. */
+#define GST_V4L2_FLOW_LAST_BUFFER GST_FLOW_CUSTOM_SUCCESS
+
+/* This flow return is used to indicated that the returned buffer was marked
+ * with the error flag and had no payload. This error should be recovered by
+ * simply waiting for next buffer. */
+#define GST_V4L2_FLOW_CORRUPTED_BUFFER GST_FLOW_CUSTOM_SUCCESS_1
+
 struct _GstV4l2BufferPool
 {
   GstBufferPool parent;

sys/v4l2/gstv4l2src.c

@@ -638,19 +638,22 @@ gst_v4l2src_create (GstPushSrc * src, GstBuffer ** buf)
 {
   GstV4l2Src *v4l2src = GST_V4L2SRC (src);
   GstV4l2Object *obj = v4l2src->v4l2object;
+  GstV4l2BufferPool *pool = GST_V4L2_BUFFER_POOL_CAST (obj->pool);
   GstFlowReturn ret;
   GstClock *clock;
   GstClockTime abs_time, base_time, timestamp, duration;
   GstClockTime delay;
 
+  do {
     ret = GST_BASE_SRC_CLASS (parent_class)->alloc (GST_BASE_SRC (src), 0,
         obj->info.size, buf);
 
     if (G_UNLIKELY (ret != GST_FLOW_OK))
       goto alloc_failed;
 
-  ret =
-      gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL_CAST (obj->pool), buf);
+    ret = gst_v4l2_buffer_pool_process (pool, buf);
+
+  } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER);
 
   if (G_UNLIKELY (ret != GST_FLOW_OK))
     goto error;
@@ -788,8 +791,15 @@ alloc_failed:
   }
 error:
   {
+    if (ret == GST_V4L2_FLOW_LAST_BUFFER) {
+      GST_ELEMENT_ERROR (src, RESOURCE, FAILED,
+          ("Driver returned a buffer with no payload, this most likely "
+              "indicate a bug in the driver."), (NULL));
+      ret = GST_FLOW_ERROR;
+    } else {
       GST_DEBUG_OBJECT (src, "error processing buffer %d (%s)", ret,
           gst_flow_get_name (ret));
+    }
     return ret;
   }
 }

sys/v4l2/gstv4l2transform.c

@@ -468,6 +468,7 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
   if (G_UNLIKELY (ret != GST_FLOW_OK))
     goto beach;
 
+  do {
     pool = gst_base_transform_get_buffer_pool (trans);
 
     if (!gst_buffer_pool_set_active (pool, TRUE))
@@ -483,6 +484,8 @@ gst_v4l2_transform_prepare_output_buffer (GstBaseTransform * trans,
     pool = self->v4l2capture->pool;
     ret = gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (pool), outbuf);
 
+  } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER);
+
   if (ret != GST_FLOW_OK) {
     gst_buffer_unref (*outbuf);
     *outbuf = NULL;

sys/v4l2/gstv4l2videodec.c

@@ -358,6 +358,7 @@ static void
 gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 {
   GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
+  GstV4l2BufferPool *v4l2_pool = GST_V4L2_BUFFER_POOL (self->v4l2capture->pool);
   GstBufferPool *pool;
   GstVideoCodecFrame *frame;
   GstBuffer *buffer = NULL;
@@ -365,6 +366,7 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
 
   GST_LOG_OBJECT (decoder, "Allocate output buffer");
 
+  do {
     /* We cannot use the base class allotate helper since it taking the internal
      * stream lock. we know that the acquire may need to poll until more frames
      * comes in and holding this lock would prevent that.
@@ -384,9 +386,9 @@ gst_v4l2_video_dec_loop (GstVideoDecoder * decoder)
       goto beach;
 
     GST_LOG_OBJECT (decoder, "Process output buffer");
-  ret =
-      gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
-          v4l2capture->pool), &buffer);
+    ret = gst_v4l2_buffer_pool_process (v4l2_pool, &buffer);
+
+  } while (ret == GST_V4L2_FLOW_CORRUPTED_BUFFER);
 
   if (ret != GST_FLOW_OK)
     goto beach;