Add WriteVideoToFile to video_file_reader.

The function checks the file extension to determine YUV or Y4M format.

Also adds a flag aligned_output_file to compare_videos.py, which allows
saving the aligned reference video to a file.

Bug: webrtc:9642
Change-Id: Ia59f5c123a1e41104756eb6b235b6581c4ffbd77
Reviewed-on: https://webrtc-review.googlesource.com/99503
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Paulina Hensman <phensman@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24787}

rtc_tools/video_file_writer.cc

@@ -0,0 +1,66 @@
+/*
+ *  Copyright (c) 2018 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 "rtc_tools/video_file_writer.h"
+
+#include <cmath>
+#include <string>
+
+#include "api/video/i420_buffer.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/refcountedobject.h"
+
+namespace webrtc {
+namespace test {
+
+void WriteVideoToFile(const rtc::scoped_refptr<Video>& video,
+                      const std::string& file_name,
+                      int fps) {
+  FILE* output_file = fopen(file_name.c_str(), "wb");
+  if (output_file == nullptr) {
+    RTC_LOG(LS_ERROR) << "Could not open file for writing: " << file_name;
+    return;
+  }
+
+  bool isY4m = rtc::ends_with(file_name.c_str(), ".y4m");
+  if (isY4m) {
+    fprintf(output_file, "YUV4MPEG2 W%d H%d F%d:1 C420\n", video->width(),
+            video->height(), fps);
+  }
+  for (size_t i = 0; i < video->number_of_frames(); ++i) {
+    if (isY4m) {
+      std::string frame = "FRAME\n";
+      fwrite(frame.c_str(), 1, 6, output_file);
+    }
+    rtc::scoped_refptr<I420BufferInterface> buffer = video->GetFrame(i);
+    const uint8_t* data_y = buffer->DataY();
+    int stride = buffer->StrideY();
+    for (int i = 0; i < video->height(); ++i) {
+      fwrite(data_y + i * stride, /*size=*/1, stride, output_file);
+    }
+    const uint8_t* data_u = buffer->DataU();
+    stride = buffer->StrideU();
+    for (int i = 0; i < buffer->ChromaHeight(); ++i) {
+      fwrite(data_u + i * stride, /*size=*/1, stride, output_file);
+    }
+    const uint8_t* data_v = buffer->DataV();
+    stride = buffer->StrideV();
+    for (int i = 0; i < buffer->ChromaHeight(); ++i) {
+      fwrite(data_v + i * stride, /*size=*/1, stride, output_file);
+    }
+  }
+  if (ferror(output_file) != 0) {
+    RTC_LOG(LS_ERROR) << "Error writing to file " << file_name;
+  }
+  fclose(output_file);
+}
+
+}  // namespace test
+}  // namespace webrtc