V4L2VideoDecodeAccelerator: implement flush by VIDIOC_DECODER_CMD.

media/gpu/v4l2_video_decode_accelerator.cc

Index: media/gpu/v4l2_video_decode_accelerator.cc
diff --git a/media/gpu/v4l2_video_decode_accelerator.cc b/media/gpu/v4l2_video_decode_accelerator.cc
index b4ac8a19f993babcca1d4833d9a59ce3e83dc9e4..fef1afd111d5dfc7285fc5849620a5d085b84434 100644
--- a/media/gpu/v4l2_video_decode_accelerator.cc
+++ b/media/gpu/v4l2_video_decode_accelerator.cc
@@ -164,6 +164,8 @@ V4L2VideoDecodeAccelerator::V4L2VideoDecodeAccelerator(
       decoder_decode_buffer_tasks_scheduled_(0),
       decoder_frames_at_client_(0),
       decoder_flushing_(false),
+      decoder_cmd_supported_(false),
+      flush_waiting_last_output_buffer_(false),
       reset_pending_(false),
       decoder_partial_frame_pending_(false),
       input_streamon_(false),
@@ -287,6 +289,8 @@ bool V4L2VideoDecodeAccelerator::Initialize(const Config& config,
     return false;
   }
 
+  decoder_cmd_supported_ = IsDecoderCmdSupported();
+
   decoder_state_ = kInitialized;
   output_mode_ = config.output_mode;
 
@@ -824,7 +828,16 @@ void V4L2VideoDecodeAccelerator::DecodeBufferTask() {
             kFlushBufferId)
       schedule_task = FlushInputFrame();
 
-    if (schedule_task && AppendToInputFrame(NULL, 0) && FlushInputFrame()) {
+    if (decoder_cmd_supported_) {
+      DVLOGF(2) << "sending decoder cmd to flush";
+      DCHECK(!flush_waiting_last_output_buffer_);
+      struct v4l2_decoder_cmd cmd;
+      memset(&cmd, 0, sizeof(cmd));
+      cmd.cmd = V4L2_DEC_CMD_STOP;
+      IOCTL_OR_ERROR_RETURN(VIDIOC_DECODER_CMD, &cmd);
+      flush_waiting_last_output_buffer_ = true;
+    } else if (schedule_task && AppendToInputFrame(NULL, 0) &&
+               FlushInputFrame()) {
       DVLOGF(2) << "enqueued flush buffer";
       decoder_partial_frame_pending_ = false;
       schedule_task = true;
@@ -1359,6 +1372,10 @@ bool V4L2VideoDecodeAccelerator::DequeueOutputBuffer() {
       // EAGAIN if we're just out of buffers to dequeue.
       return false;
     }
+    if (errno == EPIPE) {

[wuchengli, 2016/10/17 16:18:59]

We need this because this is not an error. It means no more output buffers can
be dequeued.

+      DVLOGF(3) << "Got EPIPE. Last output buffer was already dequeued.";
+      return false;
+    }
     PLOGF(ERROR) << "ioctl() failed: VIDIOC_DQBUF";
     NOTIFY_ERROR(PLATFORM_FAILURE);
     return false;
@@ -1394,6 +1411,17 @@ bool V4L2VideoDecodeAccelerator::DequeueOutputBuffer() {
       output_record.cleared = true;
     }
   }
+  if ((dqbuf.flags & V4L2_BUF_FLAG_LAST)) {
+    DVLOGF(3) << "Got last output buffer. Waiting last buffer="
+              << flush_waiting_last_output_buffer_;
+    if (flush_waiting_last_output_buffer_) {
+      // TODO(wuchengli): use V4L2_DEC_CMD_START when v4l2 core issue is
+      // addressed.
+      if (!(StopDevicePoll() && StopOutputStream() && StartDevicePoll()))
+        return false;
+      flush_waiting_last_output_buffer_ = false;
+    }
+  }
   return true;
 }
 
@@ -1531,8 +1559,10 @@ void V4L2VideoDecodeAccelerator::FlushTask() {
   TRACE_EVENT0("Video Decoder", "V4L2VDA::FlushTask");
 
   // Flush outstanding buffers.
-  if (decoder_state_ == kInitialized) {
-    // There's nothing in the pipe, so return done immediately.
+  if (!output_streamon_) {
+    // If output stream is off, output buffers are not allocated. Or the decoder
+    // is initialized, resetting or changing resolution. There's nothing in the
+    // pipe, so return done immediately.
     DVLOGF(3) << "returning flush";
     child_task_runner_->PostTask(FROM_HERE,
                                  base::Bind(&Client::NotifyFlushDone, client_));
@@ -1568,15 +1598,27 @@ void V4L2VideoDecodeAccelerator::NotifyFlushDoneIfNeeded() {
   // * All image processor buffers are returned.
   if (!decoder_input_queue_.empty()) {
     if (decoder_input_queue_.front()->input_id !=
-        decoder_delay_bitstream_buffer_id_)
+        decoder_delay_bitstream_buffer_id_) {
+      DVLOGF(3) << "Some input bitstream buffers are not queued.";
       return;
+    }
+  }
+  if (decoder_current_input_buffer_ != -1) {
+    DVLOGF(3) << "Current input buffer != -1";
+    return;
   }
-  if (decoder_current_input_buffer_ != -1)
+  if ((input_ready_queue_.size() + input_buffer_queued_count_) != 0) {
+    DVLOGF(3) << "Some input buffers are not dequeued.";
     return;
-  if ((input_ready_queue_.size() + input_buffer_queued_count_) != 0)
+  }
+  if (image_processor_bitstream_buffer_ids_.size() != 0) {
+    DVLOGF(3) << "Waiting for image processor to complete.";
     return;
-  if (image_processor_bitstream_buffer_ids_.size() != 0)
+  }
+  if (flush_waiting_last_output_buffer_) {
+    DVLOGF(3) << "Waiting for last output buffer.";
     return;
+  }
 
   // TODO(posciak): crbug.com/270039. Exynos requires a streamoff-streamon
   // sequence after flush to continue, even if we are not resetting. This would
@@ -1603,6 +1645,18 @@ void V4L2VideoDecodeAccelerator::NotifyFlushDoneIfNeeded() {
   ScheduleDecodeBufferTaskIfNeeded();
 }
 
+bool V4L2VideoDecodeAccelerator::IsDecoderCmdSupported() {
+  struct v4l2_decoder_cmd cmd;
+  memset(&cmd, 0, sizeof(cmd));
+  cmd.cmd = V4L2_DEC_CMD_STOP;
+  if (device_->Ioctl(VIDIOC_TRY_DECODER_CMD, &cmd) != 0) {
+    DVLOGF(3) "V4L2_DEC_CMD_STOP is not supported.";
+    return false;
+  }
+
+  return true;
+}
+
 void V4L2VideoDecodeAccelerator::ResetTask() {
   DVLOGF(3);
   DCHECK(decoder_thread_.task_runner()->BelongsToCurrentThread());
@@ -1722,6 +1776,7 @@ void V4L2VideoDecodeAccelerator::DestroyTask() {
   while (!decoder_input_queue_.empty())
     decoder_input_queue_.pop();
   decoder_flushing_ = false;
+  flush_waiting_last_output_buffer_ = false;
 
   if (image_processor_)
     image_processor_.release()->Destroy();
@@ -1785,6 +1840,9 @@ bool V4L2VideoDecodeAccelerator::StopOutputStream() {
   IOCTL_OR_ERROR_RETURN_FALSE(VIDIOC_STREAMOFF, &type);
   output_streamon_ = false;
 
+  // Output stream is stopped. No need to wait the buffer anymore.
+  flush_waiting_last_output_buffer_ = false;
+
   for (size_t i = 0; i < output_buffer_map_.size(); ++i) {
     // After streamoff, the device drops ownership of all buffers, even if we
     // don't dequeue them explicitly. Some of them may still be owned by the