Added tool for reference less video analysis

webrtc/tools/frame_analyzer/reference_less_video_analysis.cc

+/*
+ *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.

[kjellander_webrtc, 2016/11/23 14:44:23]

2016

[phoglund, 2016/11/23 15:19:56]

Nit: 2016

+ *
+ *  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 <vector>
+
+#include "webrtc/tools/frame_analyzer/video_quality_analysis.h"
+#include "webrtc/tools/simple_command_line_parser.h"
+
+#define NO_OF_STATS 5

[phoglund, 2016/11/23 15:19:56]

What does stats mean? I don't get it.

+#define STATS_LINE_LENGTH 28
+#define PSNR_THRESHOLD 47

[phoglund, 2016/11/23 15:19:56]

PSNR_FREEZE_THRESHOLD?

+#define SSIM_THRESHOLD .999
+
+void get_height_width_fps(int *height, int *width, int *fps,
+                          const char* video_file) {
+  /*
+   * Parse file header to get height width and fpd.
+   * File header looks like :
+   *    YUV4MPEG2 W1280 H720 F25:1 Ip A0:0 C420mpeg2 XYSCSS=420MPEG2.
+   */
+  char frame_header[STATS_LINE_LENGTH];
+  FILE* input_file = fopen(video_file, "rb");
+  fread(frame_header, 1, STATS_LINE_LENGTH, input_file);
+
+  std::string frame_header_stats[NO_OF_STATS];
+  int no_of_stats = 0;
+  char *token = strtok(frame_header, " ");
+
+  while (token != NULL) {
+    frame_header_stats[no_of_stats++] = token;
+    token = strtok(NULL, " ");
+  }
+
+  *width = std::stoi(frame_header_stats[1].erase(0, 1));
+  *height = std::stoi(frame_header_stats[2].erase(0, 1));
+  *fps = std::stoi(frame_header_stats[3].erase(0, 1));
+
+  printf("Height: %d Width: %d fps:%d \n", *height, *width, *fps);
+  fclose(input_file);
+}
+
+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: /usr/local/google/home/charujain/restore/
+         webrtc-checkout/src/webrtc/tools/test_3.y4m
+      =============================
+      Printing Identical Frames:
+        Frame Number: 29 PSNR: 48.000000 SSIM: 0.999618
+        Frame Number: 39 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
+      Total number of frames received: 74
+      Total identical frames: 5
+      Number of unique frames: 69
+      Identical continuous frames of window more than one :
+      0 0 0 0 0

[kjellander_webrtc, 2016/11/23 14:44:23]

I don't quite understand these zeros. 
Does the first 0 mean that frame 29 was identical to frame 28, but that frame 30
wasn't identical (then it would be a 1 instead) ?

+   *
+   */
+  printf("Printing Identical Frames: \n");
+
+  int total_identical_frames = 0;
+  int previous_identical_frame_number = -1;
+  int length_of_continuous_identical_frames = 0;
+  int max_length_of_identical_frames = 0;
+  std::vector<int> identical_frames;
+  int no_of_frames = PSNR_per_frame.size();
+
+  for (int i = 0; i < no_of_frames; i++) {
+    if (PSNR_per_frame[i] >= PSNR_THRESHOLD || SSIM_per_frame[i]

[phoglund, 2016/11/23 15:19:56]

This algorithm is a bit hard to read, maybe because it both counts consecutive
frames, prints them and detects if they're similar enough. What if we split up
this function a bit? I can imagine something like the following:

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());
int unique_frames = ...

That separates out most of tricky stuff out of this function.

I think you can implement the for loop simpler in the new find_frame_clusters
simpler than what you have, since you know frames are always adjacent to each
other. What about

for (each frame) {
  if (similar enough to previous frame) {
    num_frozen++;
  } else if (num_frozen > 0) {
    // Not frozen anymore.
    identical_frame_clusters.push_back(num_frozen);
    num_frozen = 0;
  }
}
if (num_frozen > 0) {
  identical_frame_clusters.push_back(num_frozen);
}

You can now easily write unit tests for find_frame_clusters as well! In fact,
try to make the print function not do any computation at all and extract all
computation to functions so you can unit test them.

+                                                          >= SSIM_THRESHOLD) {
+      printf("  Frame Number: %d PSNR: %f SSIM: %f \n", i, PSNR_per_frame[i],
+             SSIM_per_frame[i]);
+      if (previous_identical_frame_number != -1
+          && previous_identical_frame_number == i-1) {
+        length_of_continuous_identical_frames++;
+        previous_identical_frame_number = i;
+      } else {
+        max_length_of_identical_frames = std::max(max_length_of_identical_frames
+                                       , length_of_continuous_identical_frames);
+        identical_frames.push_back(length_of_continuous_identical_frames);
+        length_of_continuous_identical_frames = 0;
+      }
+      total_identical_frames++;
+    }
+  }
+  int unique_frames = no_of_frames - total_identical_frames;
+  printf("Total number of frames received: %d\n", no_of_frames);
+  printf("Total identical frames: %d\n", total_identical_frames);
+  printf("Number of unique frames: %d\n", unique_frames);
+
+  // Print identical frames if they appear together.
+  printf("Identical continuous frames of window more than one : \n");
+  for (int i = 0; i < static_cast<int>(identical_frames.size()); i++)
+    printf("%d ", identical_frames[i]);
+  printf("\n");
+}
+
+int main(int argc, char** argv) {
+  /*
+   * This script captures the freezing metrics for reference less

[phoglund, 2016/11/23 15:19:56]

I think in general avoid c-style comments. And it's not a script (which implies
bash or python)

+   * video analysis.
+   */
+  std::string program_name = argv[0];
+  std::string usage = "Outputs the freezing score by comparing current frame "
+      "with the previous frame.\nExample usage:\n" + program_name +
+      " --input_file=input_file.txt\n"
+      "Command line flags:\n"
+      "  - input_file(string): File containing absolute path of the video "
+      "files to be analyzed. Only y4m file format is supported.\n";
+
+  webrtc::test::CommandLineParser parser;
+
+  // Init the parser and set the usage message.
+  parser.Init(argc, argv);
+  parser.SetUsageMessage(usage);
+
+  parser.SetFlag("input_file", "");
+  parser.ProcessFlags();
+  if (parser.GetFlag("input_file").empty()) {
+    parser.PrintUsageMessage();
+    exit(EXIT_SUCCESS);
+  }
+  std::string video_names_file = parser.GetFlag("input_file");
+  const char * video_file = video_names_file.c_str();

[phoglund, 2016/11/23 15:19:56]

Nit: char*

+
+  FILE* video_file_ptr = fopen(video_file, "r");

[phoglund, 2016/11/23 15:19:56]

Extract 146- 215 out to a new function. Short, focused functions is good.

+  if (video_file_ptr == NULL) {
+    printf("Error opening file\n");
+    return -1;
+  }
+
+  char video_file_name[200];
+  while (fgets(video_file_name, 200, video_file_ptr)) {
+    strtok(video_file_name, "\n");
+
+    // Check for video file extension.
+    if (std::string(video_file_name).substr(strlen(video_file_name)-3, 3)
+        != "y4m") {
+      printf("Only y4m video file format are supported. Found: %s\n",
+             video_file_name);
+      return -1;
+    }
+
+    int height = 0, width = 0, fps = 0;
+    get_height_width_fps(&height, &width, &fps, video_file_name);
+
+    int no_of_frames = 0;
+    std::vector<double> PSNR_per_frame;
+    std::vector<double> SSIM_per_frame;
+    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,

[phoglund, 2016/11/23 15:19:56]

!webrtc::test::Extract...

+                                            width, height,

[phoglund, 2016/11/23 15:19:56]

Nit: indent

+                                            no_of_frames,
+                                            current_frame))) {
+        break;
+      }
+
+      if (!(webrtc::test::ExtractFrameFromY4mFile (video_file_name,
+                                            width, height,
+                                            no_of_frames+1,

[phoglund, 2016/11/23 15:19:56]

Nit: 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++;
+    }
+    printf("=============================\n");
+    printf("Printing metrics for file: %s\n", video_file_name);
+    printf("=============================\n");
+    print_freezing_metrics(PSNR_per_frame, SSIM_per_frame);
+
+    // Cleanup.
+    delete[] current_frame;
+    delete[] next_frame;
+  }
+  fclose(video_file_ptr);
+  return 0;
+}