Proof of concept using libvpx's y4minput.c

webrtc/tools/frame_analyzer/reference_less_video_analysis_lib.cc

+/*
+ *  Copyright (c) 2016 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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+#include "webrtc/tools/frame_analyzer/reference_less_video_analysis_lib.h"
+#include "webrtc/tools/frame_analyzer/video_quality_analysis.h"
+#include "third_party/libvpx/source/libvpx/y4minput.h"

[phoglund, 2016/11/30 12:41:01]

Oh, so you could just include the file. Nice! Sorry Charu, I was wrong about
that. I thought there was a problem including the file for some reason but
apparently not.

+
+#define STATS_LINE_LENGTH 28
+#define PSNR_FREEZE_THRESHOLD 47
+#define SSIM_FREEZE_THRESHOLD .999
+
+void get_height_width_fps(int *height, int *width, int *fps,
+                          const char* video_file) {
+  FILE* input_file = fopen(video_file, "rb");
+  y4m_input y4m;
+  y4m_input_open(&y4m, input_file, NULL, 0, 0);

[charujain, 2016/11/30 09:58:23]

We are using this function since this internally calls "y4m_parse_tags" which is
what we need. But since that is not directly exposed in library you are calling
this. But is this a good practise? Since this function does lot more than just
parsing. 

+
+  *width = y4m.pic_w;
+  *height = y4m.pic_h;
+  *fps = y4m.fps_n;
+  printf("Height: %d Width: %d fps:%d \n", *height, *width, *fps);
+  fclose(input_file);
+}
+
+bool frozen_frame(std::vector<double> psnr_per_frame,
+                  std::vector<double> ssim_per_frame, size_t frame) {
+  if (psnr_per_frame[frame] >= PSNR_FREEZE_THRESHOLD ||
+      ssim_per_frame[frame] >= SSIM_FREEZE_THRESHOLD)
+    return true;
+  return false;
+}
+
+std::vector<int> find_frame_clusters(std::vector<double> psnr_per_frame,
+                                     std::vector<double> ssim_per_frame) {
+  std::vector<int> identical_frame_clusters;
+  int num_frozen = 0;
+  size_t total_no_of_frames = psnr_per_frame.size();
+
+  for (size_t each_frame = 0; each_frame < total_no_of_frames; each_frame++) {
+      if (frozen_frame(psnr_per_frame, ssim_per_frame, each_frame)) {
+        num_frozen++;
+        } else if (num_frozen > 0) {
+          // Not frozen anymore.
+            identical_frame_clusters.push_back(num_frozen);
+            num_frozen = 0;
+        }
+  }
+  return identical_frame_clusters;
+}
+
+void print_freezing_metrics(std::vector<double> psnr_per_frame,
+                            std::vector<double> ssim_per_frame) {
+  /*
+   * Prints the different metrics mainly:
+   * 1) Identical frame number, PSNR and SSIM values.
+   * 2) Length of continuous frozen frames.
+   * 3) Max length of continuous freezed frames.
+   * 4) No of unique frames found.
+   * 5) Total different identical frames found.
+   *
+   * Sample output:
+   *  Printing metrics for file: /src/webrtc/tools/test_3.y4m
+      =============================
+      Total number of frames received: 74
+      Total identical frames: 5
+      Number of unique frames: 69
+      Printing Identical Frames:
+        Frame Number: 29 PSNR: 48.000000 SSIM: 0.999618
+        Frame Number: 30 PSNR: 48.000000 SSIM: 0.999898
+        Frame Number: 60 PSNR: 48.000000 SSIM: 0.999564
+        Frame Number: 64 PSNR: 48.000000 SSIM: 0.999651
+        Frame Number: 69 PSNR: 48.000000 SSIM: 0.999684
+      Print identical frame which appears in clusters :
+        2 1 1 1
+   *
+   */
+  size_t total_no_of_frames = psnr_per_frame.size();
+  std::vector<int> identical_frame_clusters = find_frame_clusters(
+        psnr_per_frame, ssim_per_frame);
+  int total_identical_frames = std::accumulate(
+      identical_frame_clusters.begin(), identical_frame_clusters.end(), 0);
+  size_t unique_frames = total_no_of_frames - total_identical_frames;
+
+  printf("Total number of frames received: %zu\n", total_no_of_frames);
+  printf("Total identical frames: %d\n", total_identical_frames);
+  printf("Number of unique frames: %zu\n", unique_frames);
+
+  printf("Printing Identical Frames: \n");
+  for (size_t frame = 0; frame < total_no_of_frames; frame++) {
+    if (frozen_frame(psnr_per_frame, ssim_per_frame, frame)) {
+      printf("  Frame Number: %zu PSNR: %f SSIM: %f \n", frame,
+             psnr_per_frame[frame], ssim_per_frame[frame]);
+    }
+  }
+
+  printf("Print identical frame which appears in clusters : \n");
+  for (int cluster = 0;
+      cluster < static_cast<int>(identical_frame_clusters.size()); cluster++)
+    printf("%d ", identical_frame_clusters[cluster]);
+  printf("\n");
+}
+
+void compute_metrics(std::string video_file_name,
+                     std::vector<double>* psnr_per_frame,
+                     std::vector<double>* ssim_per_frame) {
+  int height = 0, width = 0, fps = 0;
+  get_height_width_fps(&height, &width, &fps, video_file_name.c_str());
+
+  int no_of_frames = 0;
+  int size = webrtc::test::GetI420FrameSize(width, height);
+
+  // Allocate buffers for test and reference frames.
+  uint8_t* current_frame = new uint8_t[size];
+  uint8_t* next_frame = new uint8_t[size];
+
+  while (true) {
+    if (!(webrtc::test::ExtractFrameFromY4mFile (video_file_name.c_str(),
+                                                 width, height,
+                                                 no_of_frames,
+                                                 current_frame))) {
+      break;
+    }
+
+    if (!(webrtc::test::ExtractFrameFromY4mFile (video_file_name.c_str(),
+                                                 width, height,
+                                                 no_of_frames + 1,
+                                                 next_frame))) {
+      break;
+    }
+
+    double result_psnr = webrtc::test::CalculateMetrics(webrtc::test::kPSNR,
+                                                        current_frame,
+                                                        next_frame,
+                                                        width, height);
+    double result_ssim = webrtc::test::CalculateMetrics(webrtc::test::kSSIM,
+                                                        current_frame,
+                                                        next_frame,
+                                                        width, height);
+
+    psnr_per_frame->push_back(result_psnr);
+    ssim_per_frame->push_back(result_ssim);
+    no_of_frames++;
+  }
+  // Cleanup.
+  delete[] current_frame;
+  delete[] next_frame;
+}
+
+bool check_file_extension(std::string video_file_name) {
+  if (video_file_name.substr(video_file_name.length()-3, 3) != "y4m") {
+    printf("Only y4m video file format is supported. Given: %s",
+           video_file_name.c_str());
+    return false;
+  }
+  return true;
+}
+
+int run_analysis(std::string video_file) {
+  std::vector<double> psnr_per_frame;
+  std::vector<double> ssim_per_frame;
+  if (check_file_extension(video_file)) {
+    compute_metrics(video_file, &psnr_per_frame, &ssim_per_frame);
+  } else {
+    return -1;
+  }
+  printf("=============================\n");
+  printf("Printing metrics for file: %s\n", video_file.c_str());
+  printf("=============================\n");
+  print_freezing_metrics(psnr_per_frame, ssim_per_frame);
+  return 0;
+}