Specifications And Recommendations For Generating A Video Source File

1. Specifications And Recommendations For Generating A Video Source File Suitable for streaming video to the Internet and mobile devices through the Streamlike platform Tools for quality control of a video source file Version 1.1 – 17/08/2011

2. Executive Summary • As an opening we provide a shortlist of important recommendations presented later on in this document for generating your video source file. • H.264 export - MPEG4AVC video codec and AAC audio codec in a .mp4 wrapper • “High” H.264 Profile with CABAC enabled and 2 pass encoding • Frame rate identical to the your original video component • One key frame per second (also known as “I frame”) • Video bit rate at 6000Kbps for a recommended video format of 1280x720 (“720p” HD) using VBR (variable bit rate). See page 4 for other video format • Audio bit rate at 192Kbps with a sample rate of 48kHz. LC AAC profile • Maintain pixel aspect ratio “1:1” (square pixels) Contents Executive Summary…………………………………………………………… ………. 2 Why Should I Care About The Specifications Of My Video Source File?......... 3 Video Source File Specifications and Recommendations…………………….. 4 Observing Specifications And Quality Control Of A Video Source File……... 6 Contact………………………………………………………………………..... ………. 9 2

3. Why Should I Care About The Specifications Of My Video Source File? • When producing a video from your editing software application (Final Cut series, Adobe Premiere series, iMovie …) you export a video source file that will be used as a source for all future encodings to reach viewers accessing the Internet over PC, Mac or mobile devices. • As we re-encode an already encoded file it is important to properly encode your video source file to obtain the best possible quality for all future encodings. • Depending on the editing software application your are using you could encounter different issues affecting playback of your video source file: • A video or audio codec may be missing to allow playback or encoding. Using mediainfo (see page 6) you can easily identify missing codecs and outreach to the Internet to install the missing ones • Incoherent or mis-interpreted meta-data: this problem could occur for example when using software part of the Adobe CS4 suite for which the .mp4 wrapper include a large number of tags that are not necessary for online streaming and often mis-interpreted by encoders. This issue can also be faced when exporting video through the Final Cut suite when a .mov wrapper is used. For this reason we recommend you use the official MPEG4 wrapper (.mp4) when exporting from a Final Cut software • Different audio and video lengths: this could happen as video files sustain multiple encodings or when the gap between key frames is too large (keyframes are least compressible but don't require other video frames to decode). In this case it may be necessary to start from scratch and generate a new video source file from an untouched original recording or if not available work using an AVI or MJPEG format that allow for re-synchronizing audio and video. • Different information for the display aspect ratio (often 4:3 or 16:9) and the actual format of the video file. For source files that are anamorphic - meaning the video has to be warped during playback to meet the display aspect ratio this discrepancy of information is on purpose. As an example a DV video will retain a video format of 720x576 regardless of the display aspect ratio being 4:3 or 16:9. 3

4. Had this video been recorded in 16:9 the video player would need to upscale the width of the picture to 1024 px or downscale the height of the picture to 404 px to retrieve a 16:9 display aspect ratio. We refer to a video with non-square pixels in this case. As many online or offline video players do not properly decode anamorphic videos (as one can regularly see distorted videos on YouTube, Dailymotion or Brightcove) it is our recommendation that you produce your video source file with square pixels Video Source File Specifications And Recommendations • It is now a widely accepted practice in the Internet industry to export video source file using H.264 (MPEG4AVC video codec and AAC audio codec) in a .mp4 wrapper. • Frame rate and key frames: • We recommend you always select the same frame rate as your original video component. Most of the time it would be 25 fps (Europe) or 30 fps (north America). If your editing software application allows you to set spacing between key frames we suggest to opt for one key frame per second that is to say every 25 or 30 frames. • Video bit rate • This setting affects both the quality of your video output and the size of your video file. Video bitrates are measured using Kbps (kilobits per second). Here are target video bitrates we recommend based on your video format: • Standard DV - 720x576 or 720x480 video format: 2500Kbps • - Widescreen DV - 1024x576 or 1024x480 video format: 3800Kbps • - High definition « 720p » - 1280x720: 6000Kbps • - High definition « 1080i or 1080p » - 1920x1080: 13500Kbps • Select variable video bit rate for your encoding (VBR) 4

5. Resizing: Unless you have a specific requirement for your video source file it is our recommendation to stop at “720p” video format when considering delivery to the Internet in order to reach a wider audience. You may need to downscale the video format of your original video component when generating your video source file. As explained above we highly recommend you generate a video source file with square pixels (pixel aspect ratio 1:1). When exporting your video source file you need to resize the height and the width to obtain an identical ratio as your original video component. Compression algorithms will render better results when the height and the width of your video can be divided by 16. The reason being that spatial compression often applies to square blocks of 16x16 pixels also know as macroblocks. The only two video formats with a 16:9 ratio for which both width and height can be divided by 16 are 1024x576 and 1280x720. Deinterlacing: When available this setting is always recommended especially if the recording format is DV or similar. Different recordings can produce different types of interlacing and it may be necessary to employ specific software to gain access to an efficient deinterlacing algorithm. If an inappropriate deinterlacing method is apply to a video it will create undulation especially visible on moving objects or persons whereas no deinterlacing would mean an horizontal combing effect on your video source file. Audio: We recommend you encode your video at 192kbps audio bit rate using a sample rate of 48kHz and opting for the LC AAC profile. Encoding video profile: Using H.264 you will be generally presented with 3 different profiles: “baseline” “main” and “high”. Higher profile will induce more demanding decoding resources but will render better quality for your video source file. 5

6. To generate a video source file for broadcasting to the Internet you should always opt for the “high” H.264 profile. “Baseline” profile is used for encoding to mobile devices which only have limited decoding resources. We do use H.264 “baseline” profile when encoding for mobile devices through the Streamlike platform using a H.264 “high” profile video source file. • Advanced settings: • We present in this section some further recommended specifications that could be available with your editing software application. • We recommend you always choose 2 pass encoding for your video source file. This normally means a reasonably longer encoding time but a significant gain in quality at identical video file size. First pass is used for analyzing the video file (bits are better distributed to maintain constant quality) to prepare the actual encoding that takes place during pass two. • Two encoding modes are available with H.264: CABAC or CAVALC. To generate your video source file you will want to opt for CABAC mode when available (CABAC mode is not supported by Apple Compressor). • When given the choice you can use B-frames and use them as reference frames. • Here are our recommendations for the following settings when available: • Multi-layer = -2 • reference frames = 4 • search shape = 8x8 • Subpixel mode = quarter • Multi reference frame estimate = fast • Sub block motion estimate = yes • Hadamard transformation = yes • Deblocking = yes Observing Specifications And Quality Control Of A Video Source File Using VLC (www.videolan.org/vlc/) you can hit CTRL+J or go to Tools > Codec Information while playing your video to gain access to its specifications. A more complete tool is Mediainfo (http://mediainfo.sourceforge.net/en) a free software that thoroughly details the audio and video specifications of your video source file . 6

7. Information obtained through those software normally allow your to detect discrepancies or anomalies causing issues to your video source file for playback or encoding. Below is an example of information obtained through those two software for the same video source file: Using VLC: The tab containing interesting information is Codec Details. The Statistics tab is dynamically updated while playing your video. 7

8. Using Mediainfo : You can choose to display format as text or html to collect all available information and copy/paste them in another document. 8

9. Contacts Mediatech - Streamlike2 Ter Villa Thoréton 75015 ParisFrance Phone: (33) 1 83 79 01 62 Email: europe@streamlike.com 9