Add support for a forced software encoder fallback.

webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.cc

 /* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
 
 #include "webrtc/modules/video_coding/codecs/vp8/default_temporal_layers.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include <algorithm>
 #include <vector>
 
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/modules/video_coding/codecs/vp8/include/vp8_common_types.h"
 #include "webrtc/modules/video_coding/include/video_codec_interface.h"
 #include "webrtc/rtc_base/checks.h"
+#include "webrtc/system_wrappers/include/field_trial.h"
 
 #include "vpx/vpx_encoder.h"
 #include "vpx/vp8cx.h"
 
 namespace webrtc {
 
 TemporalLayers::FrameConfig::FrameConfig()
     : FrameConfig(kNone, kNone, kNone, false) {}
 
 TemporalLayers::FrameConfig::FrameConfig(TemporalLayers::BufferFlags last,
@@ skipping 209 matching lines @@
                   TemporalLayers::kReference, TemporalLayers::kFreezeEntropy)};
     default:
       RTC_NOTREACHED();
       break;
   }
   RTC_NOTREACHED();
   return {TemporalLayers::FrameConfig(
       TemporalLayers::kNone, TemporalLayers::kNone, TemporalLayers::kNone)};
 }
 
+// Temporary fix for forced SW fallback.
+// For VP8 SW codec, |TemporalLayers| is created and reported to
+// SimulcastRateAllocator::OnTemporalLayersCreated but not for VP8 HW.

[brandtr, 2017/08/04 11:16:24]

Should we file a bug to track this issue?

[sprang_webrtc, 2017/08/07 08:59:12]

Why did explicitly de-registering the temporal layers instance in the encoder
destructor not work?

[åsapersson, 2017/08/08 10:40:54]

Using something like tl_factory->Remove is not possible from the encoder since
the SimulcastRateAllocator might be destructed by then and the
TemporalLayerFactory (owned by SimulcastRateAllocator).

[sprang_webrtc, 2017/08/09 08:38:07]

Ah, that's problematic. This should be fixed, but let's do that in a separate
cl.

+// Causes any issue when going from forced SW -> HW as |TemporalLayers| is not
+// deregistred when deleted by SW codec (tl factory might not exist, owned by
+// SimulcastRateAllocator).
+bool ExcludeOnTemporalLayersCreated(int num_temporal_layers) {
+  return webrtc::field_trial::IsEnabled("WebRTC-VP8-Forced-Fallback-Encoder") &&
+         num_temporal_layers == 1;
+}
 }  // namespace
 
 DefaultTemporalLayers::DefaultTemporalLayers(int number_of_temporal_layers,
                                              uint8_t initial_tl0_pic_idx)
     : num_layers_(std::max(1, number_of_temporal_layers)),
       temporal_ids_(GetTemporalIds(num_layers_)),
       temporal_layer_sync_(GetTemporalLayerSync(num_layers_)),
       temporal_pattern_(GetTemporalPattern(num_layers_)),
       tl0_pic_idx_(initial_tl0_pic_idx),
       pattern_idx_(255),
@@ skipping 104 matching lines @@
     vp8_info->tl0PicIdx = tl0_pic_idx_;
   }
 }
 
 TemporalLayers* TemporalLayersFactory::Create(
     int simulcast_id,
     int temporal_layers,
     uint8_t initial_tl0_pic_idx) const {
   TemporalLayers* tl =
       new DefaultTemporalLayers(temporal_layers, initial_tl0_pic_idx);
-  if (listener_)
+  if (listener_ && !ExcludeOnTemporalLayersCreated(temporal_layers))
     listener_->OnTemporalLayersCreated(simulcast_id, tl);
   return tl;
 }
 
 void TemporalLayersFactory::SetListener(TemporalLayersListener* listener) {
   listener_ = listener;
 }
 
 }  // namespace webrtc