Generate a side-by-side comparison video from two WebPageTest runs.

wpt-side-by-side

#!/usr/bin/env bash
#
# wpt-side-by-side
# ~~~~~~~~~~~~~~~~
# Generate a side-by-side comparison video from two WebPageTest runs.
#
# Usage:
#   wpt-side-by-side WEBPAGETEST_URL_1 WEBPAGETEST_URL_2
#
# Requirements:
#   * ffmpeg
#   * ffmpeg2theora
#
# Example:
#   wpt-side-by-side \
#     http://www.webpagetest.org/result/150731_4N_16RK/ \
#     http://www.webpagetest.org/result/150817_EJ_1DZW/
#
# This will generate combined_150731_4N_16RK_150817_EJ_1DZW.{mp4,ogv}
#
# Copyright (C) 2015 Ori Livneh <ori@wikimedia.org>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
set -e

usage() {
  echo >&2 "Usage: $0 TEST_URL_1 TEST_URL_2"
}


get_test_id() {
  # Extract the WebPageTest test ID from a WebPageTest URL
  grep -Po '\d{6}_\w{2}_\w{4}' <<<"$*"
}


get_video() {
  # Download the video for a given WebPageTest run
  local test_id="$(get_test_id "$1")"
  curl -s "http://www.webpagetest.org/video/download.php?id=${test_id}.1.0" -o "${test_id}.mp4"
  echo "${test_id}.mp4"
}


combine_videos() {
  # Combine two WebPageTest run videos into a single OGV file
  local target_name="combined_$(basename "$1" .mp4)_$(basename "$2" .mp4)"
  ffmpeg -i "$1" -i "$2" -filter_complex \
    "[0:v] setpts=PTS-STARTPTS, pad=iw*2:ih [left]; \
     [1:v] setpts=PTS-STARTPTS [right]; \
     [left][right] overlay=w" "${target_name}.mp4"
  ffmpeg2theora "${target_name}.mp4" --noaudio -v 10
  echo "${target_name}.ogv"
}


if [[ $# -ne 2 ]] || ! get_test_id $1 >/dev/null || ! get_test_id $2 >/dev/null ; then
  usage
  exit 1
fi

left="$(get_video "$1")"
right="$(get_video "$2")"
combine_videos "$left" "$right"