Implement NullVideoDecoder to avoid crash on unsupported decoders.

webrtc/video/video_decoder.cc

 /*
  *  Copyright (c) 2015 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/video_decoder.h"
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/video_coding/codecs/h264/include/h264.h"
 #include "webrtc/modules/video_coding/codecs/vp8/include/vp8.h"
 #include "webrtc/modules/video_coding/codecs/vp9/include/vp9.h"
 
 namespace webrtc {
 VideoDecoder* VideoDecoder::Create(VideoDecoder::DecoderType codec_type) {
   switch (codec_type) {
     case kH264:
       RTC_DCHECK(H264Decoder::IsSupported());
       return H264Decoder::Create();
     case kVp8:
       return VP8Decoder::Create();
     case kVp9:
       return VP9Decoder::Create();
     case kUnsupportedCodec:
-      RTC_NOTREACHED();
-      return nullptr;
+      return new NullVideoDecoder();

[pbos-webrtc, 2016/02/02 13:59:13]

I'd prefer a log here as well.

[joachim, 2016/02/02 14:31:33]

Done.

   }
   RTC_NOTREACHED();
   return nullptr;
 }
 
 VideoDecoder::DecoderType CodecTypeToDecoderType(VideoCodecType codec_type) {
   switch (codec_type) {
     case kVideoCodecH264:
       return VideoDecoder::kH264;
     case kVideoCodecVP8:
@@ skipping 97 matching lines @@
     return fallback_decoder_->PrefersLateDecoding();
   return decoder_->PrefersLateDecoding();
 }
 
 const char* VideoDecoderSoftwareFallbackWrapper::ImplementationName() const {
   if (fallback_decoder_)
     return fallback_implementation_name_.c_str();
   return decoder_->ImplementationName();
 }
 
+NullVideoDecoder::NullVideoDecoder() {}
+
+int32_t NullVideoDecoder::InitDecode(const VideoCodec* codec_settings,
+                                     int32_t number_of_cores) {
+  LOG(LS_ERROR) << "Can't initialize NullVideoDecoder.";
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t NullVideoDecoder::Decode(const EncodedImage& input_image,
+    bool missing_frames,
+    const RTPFragmentationHeader* fragmentation,
+    const CodecSpecificInfo* codec_specific_info,
+    int64_t render_time_ms) {
+  LOG(LS_ERROR) << "The NullVideoDecoder doesn't support decoding.";
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t NullVideoDecoder::RegisterDecodeCompleteCallback(
+    DecodedImageCallback* callback) {
+  LOG(LS_ERROR)
+      << "Can't register decode complete callback on NullVideoDecoder.";
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t NullVideoDecoder::Release() {
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+int32_t NullVideoDecoder::Reset() {
+  return WEBRTC_VIDEO_CODEC_OK;
+}
+
+const char* NullVideoDecoder::ImplementationName() const {
+  return "null";

[noahric, 2016/02/02 14:06:43]

Maybe NullVideoDecoder, so the logging doesn't look weird ("why is this logging
null? is it actually null?").

[joachim, 2016/02/02 14:31:33]

Done.

+}
+
 }  // namespace webrtc