Questions. Encoding for Multiple Screen Delivery. Jan Ozer

Transcription

1 Encoding for Multiple Screen Delivery Jan Ozer Questions Most information derived from 0For more information, check out the book Published, April 2013

2 Agenda Terms and terminology Producing H.264 Finding the optimal video configuration Introduction to adaptive streaming Choosing a delivery technology Producing for adaptive streaming If you see red, pay attention Terms and Terminology Codec/compression Bandwidth Resolution Data rate Bitrate control Container formats, program and transport streams

3 Compression/Codec Compression Used to shrink the size of video/audio still images Common codecs Video - H.264/AVC, H.265/HEVC, WebM, MPEG-2 Audio - MP3, AAC, WMV Still image - JPG, PNG, GIF Codecs - all of the above Any technology that COmpresses in the studio, then DECompresses in the field Why is Compression Important? To achieve the target data rate, you have to compress Compression is lossy, the more you compress, the more you lose This is immutable

4 About Bandwidth What is bandwidth? Viewer s connection speed Why is it important? Controls your viewer s ability to retrieve and play video smoothly Higher delivery bandwidths mean higher data rates, which means better quality Bandwidth - Where Are We? Viewer s connection speed to the Internet Average download speeds per Akamai State of the Internet: US - 7,611 kbps Canada - 6,607 kbps Mexico - 2,941 kbps UK - 6,470 kbps France - 4,804 kbps So why does CNN max out at 1,200 kbps?

5 Paradigm Shift Modem connection speeds (28.8/56 kbps) Make the video fit Broadband Make it good enough Make it affordable CNN is at 1,200 kbps; not to fit pipes, but because it s good enough and affordable Cellular Make it fit About Resolution What is it? Actual pixels in the file

6 Resolutions That We Know and Love Acquisition DV - 720x p x i/p x1080 Distribution DVD - 720x480 Streaming p or smaller ipod/iphone/ipad - 320x p Why is Resolution Important Most video starts life at 720p or higher Streamed at 320x180 to 1080p Resolution is key quality factor At a set bit rate, increasing resolution degrades quality because you must compress more pixels Can t say that 1,200 kbps is adequate without knowing resolution For 640x360x25, it s adequate For 1080p, it s not

7 What is Data Rate? Amount of data per second of video Largely determines video quality At static resolution and frame rate, increasing bit rate increases quality Largely determines bandwidth costs 800 kbps Constant vs Variable Bit Rate VBR 500 kbps CBR 300 kbps Low Motion Moderate Motion Low Motion Moderate Motion High Motion

8 VBR vs. CBR Constant vs Variable Bit Rate Constant Bit Rate (CBR) One bit rate applied to entire video, irrespective of content Pros: Computationally easy Fast - one pass will do it Cons: Doesn't optimize quality

9 Constant vs Variable Bit Rate Variable Bit Rate (VBR) Dynamic bit rate matches motion in video Pros: Best quality Cons: Need two or more passes Can produce stream with significant variability How do I Produce the Best Quality CBR? Use 2-pass CBR when available Scans file (like VBR), but packs data into a consistent stream Best of both worlds when available 1-pass of live or draft work

10 How Do I Produce the Optimal VBR File? 2 passes or more Use Constrained Constrains to data rate to specified max Set Target and Max/Min Overall target 500 kbps Max/Peak bit rate how high rate can go when varying Rule of thumb is 1.5-2X of target If minimum setting, use.5x When Should I Use VBR/CBR? VBR Constrained VBR (usually 2X) for most streaming applications Broadband delivery can handle spikes Constrained VBR for virtually all progressive delivery Constrained VBR for most cellular, though not universal CBR CBR for live, particularly when limited outbound bandwidth CBR or constrained VBR for adaptive streaming (more later)

11 Container Formats, Transport Streams, Program Streams Container format: A meta-file format whose specification describes how data and metadata are stored Examples: MPG, MP4, MOV, F4V, WMV, FLV Transport stream: Transport stream specifies a container format encapsulating packetized elementary streams, with error correction and stream synchronization features for maintaining transmission integrity when the signal is degraded (e.g. - broadcast) Examples:.ts, Why Do We Care? When producing for single file or adaptive delivery, you must choose the right container format/transport stream for your application Streaming Flash - MP4, FLV, F4V, MOV - H.264 HTML5 - MP4 - H.264, WebM - VP8 idevices - MP4, MOV - H.264 Adaptive - HTTP Live Streaming -.ts

12 Questions on Terms and Terminology? Should be 9:25 Download presentation handouts At Producing H.264 Introduction to H.264 H.264 encoding parameters

13 Introduction to H.264 The MPEG-4 specification The MPEG-4 codec MPEG-4 spec audio options The H.264 codec H.264 Basics Preload MPEG-4 Specification Introduced in 1998 by ISO/IEC Moving Picture Experts Group 28 Parts within specification Part 2 - MPEG video codec (the MPEG-4 codec) Part 3 - MPEG-4 audio (AAC, etc) Part 10 - Advanced Video Coding (AVC/H.264) Part 14 - container format (MP4)

14 The MPEG-4 Video Codec Used only for low power devices: Two profiles: Simple Profile - very low power, low bandwidth applications Advanced Simple Profile - Simple plus: Support for "MPEG"-style quantization Support for B pictures (a.k.a. B-frames) Motion compensation Check specs on target devices Will refer to MPEG-4 encoding only in mobile segments Never use for computer playback MPEG-4 Audio AAC-Low Complexity (AAC-LC) The most basic and most broadly compatible In my tests, indistinguishable from HE AAC/HE AACv2 High Efficiency AAC (2003) Also called AAC+ and aacplus High Efficiency AACv2 (2006) Also called enhanced AAC+, aacplus v2 and eaac+

15 MPEG-4 Audio Summary Recommendations Usage dictated by specs of target device When producing for multiple devices, use lowest common denominator When in doubt, choose AAC-LC Most compatible on the playback side Universally available on MPEG-4/H.264 encoders What is H.264? Streamcrest Associates Adapted by ISO and ITU Telephony/cellular TV - consumer electronics Computer electronics Only codec adopted by top three streaming providers (Apple, Adobe, Microsoft)

16 What's MPEG-4/H.264 Cost? For free Internet video (e.g. no subscription or pay per view), free in perpetuity Thank you Google (WebM) Still technically an obligation to sign a license, but there are no teeth and no motivation to enforce For subscription or PPV, there may be a royalty obligation Check The Many Wrappers of H.264.MP4 - official MPEG-4 wrapper.m4v - Apple s variant for itunes and devices.mov - H.264 file for editing or QuickTime delivery.f4v - H.264 for Flash.3GP - (not shown) - phone.mpg - H.264 in MPEG-2 transport stream

17 H.264 Encoding Parameters The basics I, B and P-frames Search-related options Miscellaneous options H.264 Encoding - Basics Profiles and Levels Entropy encoding

18 What are H.264 Profiles? Define a set of coding tools or algorithms that can be used in generating a bitstream Profiles and Playback Compatibility Profile PreiPhone 4 Android 3.0 Software Android Hardware ipad 1 iphone 4-5 ipad 2/3 Using the wrong profile results in a file incompatible with your target Need to know profile of target device and choose appropriate profile Some interesting decisions to make when encoding for multiple device delivery Flash/ HTML5 Baseline Yes Yes Yes Yes Yes Yes Yes Main No No? Yes Yes Yes Yes High No No? No Yes Yes Yes

19 Quality-Related Expectations Baseline profile - fewest advanced algorithms: Lowest quality stream Easiest to encode and particularly decode High profile most advanced algorithms Highest quality stream Hardest to encode/decode Why Do Profiles Exist? Meeting point for hardware vendor and video producer Example: Original video capable ipod is baseline only: why? Lower power (cheaper) CPU Less power consumption Video producer: to produce that will play on ipod, use Baseline profile

20 Rule Number 1 Don t exceed profile of target device Exclusively a concern with mobile Computers and OTT devices can play High profile (any level) Required Profiles for idevices Original ipod (to-5g) ipod nano/ classic/ ipod touch/iphone to V4 iphone 4 /ipod touch 4/ ipad 1&2 iphone 4S IPhone 5/ New ipad Video codec H.264 H.264 H.264 H.264 H.264 Profile/level Baseline to Level 1.3 Baseline to Level 3.0 Main to Level 3.1 High to Level 4.1 High to Level 4.1 Max video data rate 768 kbps 2.5 Mbps 14 Mbps 50 Mbps 62.5 mbps for level Max video resolution 320x x p 1080p 108p Frame rate 30 fps 30 fps 30 fps 30 fps 30 fps Audio codec AAC-LC AAC-LC AAC-LC AAC-LC AAC-LC Max audio data rate 160 kbps 160 kbps 160 kbps 160 kbps 160 kbps Audio params 48 khz, stereo 48 khz, stereo 48 khz, stereo 48 khz, stereo 48 khz, stereo Four playback classes Must configure video appropriately to play on target

21 Required Profiles for Android These recommendations are least common denominator software-only playback Most devices probably more capable (no table because too many manufacturers) For 100% compatibility, use these Required Profiles for Windows 8 Phones H.264-encoded video in MP4 container Files s/not exceed params for 7x27a CPU.

22 Profiles and Playback Compatibility Profile PreiPhone 4 Android 3.0 Software Android Hardwar e ipad 1 iphone 4-5 Win 8 Phone ipad 2/3 PCs/ note books Baseline Yes Yes Yes Yes Yes Yes Yes Yes Yes Main No No? Yes Yes Yes Yes Yes Yes High No No? No Yes Yes Yes Yes Yes OTT Using the wrong profile produces a file incompatible with your target Need to know profile of target device and choose appropriate profile Big Decision #1 One set of files all Baseline that plays everywhere? Cheapest, easiest Separate files: Baseline Very old ios and Android Main Old ios and Android High new ios, computers and OTT Optimal quality, but more encoding, storage and administrative

23 What is the Quality Difference? Consulting project questions Is it worth creating two sets of files, one for mobile (with Baseline and Main), the other for Desktop (High)? How much difference quality? Ran comparisons at aggressive data rates: kbps (Burberry is at 3 mbps) 500 kbps (CNN is at 1200 kbps) 240 kbps Does Profile Matter?

24 Does Profile Matter? The Bottom Line At kbps: Some noticeable differences appear at these extreme encoding parameters

25 The Bottom Line Key takeaway: The quality difference may be less than you would expect Two sets of files, one for mobile, one for desktop/ott? Test quality difference at most extreme rates and see if the quality difference warrants it This client used all Baseline What are H.264 Levels? Constrains key parameters in the bitstream

26 H.264 Levels-Devices Critical not to exceed level of target device Devices won t load file encoded beyond max supported level So, make sure encoding parameters don t exceed level (most templates do this) H.264 Levels Desktops Flash/HTML5 players will load and attempt to play all profiles/all levels Exceeding a certain level won t kick the file out like devices If resolution too large, file won t play smoothly Up to 848x480 will play smoothly on most computers 720p may not play on some older/slower computers Don t use 720p and higher unless you re offering adaptive (or otherwise multiple) streams

27 Entropy Encoding CABAC (Context-adaptive binary arithmetic coding) More efficient (e.g. better quality), but harder to decode Main/High profile only CAVLC (Context-adaptive variable-length coding) Less efficient, easier to decode What Would YouTube Do? High Profile CABAC

28 I-, B- and P-frames Caveats: Presented differently by each encoding tool Will only cover most important and most common parameters What are I, B and P Frames? I-Frame - encoded without reference to other frames (also called Key Frames) P - looks backward to I and P frames (predictive) B - looks forward and backward to previous I and P frames (Bi-directional interpolated) No frames refer to B-Frame (most of the time)

29 Configuring Key Frames Least efficient so largest (which is bad) But, key frames enhance interactivity All playback starts on a key frame When seeking to random frame, must start playback at key frame Maximum interval should be 5-10 seconds Key frames "reset" quality: Useful at scene changes Enable natural key frames or key frames at scene changes Configuring Key Frames Rules change completely when encoding a group of files for adaptive streaming Shorter key frame interval Disable scene change detection

30 Configuring B Frames? Main/High profiles only The most efficient frame So improves quality (comparisons to come) Hardest to decode Decoder has to have all referenced frames in memory to decode B-frame Frame usually delivered out of order, which also complicates playback Typical B-Frame Encoding Parameters Number is number of B frames between I and P-Frames; (IBBBPBBBPBBBPBBBP) 3 is recommended Reference frames (both P and B-frames) Number of frames searched for redundancies 5 is recommended setting

31 Do B-Frames Matter? YouTube does NOT use B- frames with many H.264 files it produces Though they are used with some encodes My tests in Episode with 0, 1, 3 and 5 B-frames 640x480@468 kbps 1280x720@800 kbps Showed very, very little difference (and then only in HD clip) HD Comparisons

32 Do B-Frames Matter? Do B-Frames Matter?

33 B-Frame Bottom Line 3 B-frames/5 reference frames is a good general purpose recommendation Don t spend a lot of time worrying about optimal B-frame settings, because for most videos, it probably wouldn t make that much of a difference Advanced Frame Options IDR frames Two kinds of key frames IDR key frame no frame can reference frame before key frame Non-IDR key frames B- and P-frames can reference frames before key frame All key frames should be IDR key frames in streaming files

34 Advanced Frame Options Adaptive B-frames adapt frame type to improve quality Always enable Reference B-pictures Allows P-frames to reference B-frames Enable for optimal quality Pyramid B-frame allows B-frames to reference other B-frames Enable for optimal quality Search Related Options Searching for redundancies; multiple factors Search shape (8x8/16x16) size of shape used for searching (smaller is more accurate Sub-pixel mode (full/half/quarter pixel) smaller is more accurate Fast - trades encoding speed for quality

35 Slices Divides frame into segments to speed encoding Assign a CPU to each slice But: Search for redundancies occurs within each slice If lots of inter-slice motion, encoder won t find these redundancies Using slices can reduce quality Set to lowest value (either 0 or 1) Reflections on the Utility of H.264 Tweaking Less is more Many high-end hardware encoders offer minimal H.264 config options Elemental (right) Envivio Make most configuration decisions for you

36 As We ve Seen Profile matters very little B-frames matters very little Where to Focus Your Attention? Get the config right Rez/data rate/key frames Choose the right H.264 codec (x264 > MC > Apple) You ve captured 98% of potential quality

37 Does it all Matter Tweaking Relevance As data rates increase, the impact of H.264- related tweaking goes down Low Data Rate High Synthesis Focus heavily on finding the optimal configuration for your video Don t mess up anything else De-interlacing Aspect ratio Bitrate control Then, if you have the time, worry about tweaking to get the last 1-5%

38 Questions on H.264 Should be 10:20 Download presentation handouts At Finding the Optimal Configuration Understanding bits/pixel Applying bits/per pixel

39 Why Bits/Pixel is Relevant Which of these firms would you take videorelated configuration advice from? Kind of tough to compare, isn t it? Why Bits/Pixel is Relevant This adds some data, but how do they really compare compression-wise?

40 Why Bits/Pixel is Relevant How about now? Accenture s bits/pixel is almost 7 times higher Bits Per Pixel How much data applied to each pixel in video file To calculate: Data rate/(fps*pixels) Or, get MediaInfo Calculates for you, plus lots of other file details mediainfo.sourceforge.net/en

41 Bits Per Pixel In general At 640x360 or smaller, values above.2 almost clearly a waste CNN is about.121 for low motion ESPN maxes at.201, but that s for sports Values drop as videos get larger (codecs work more efficiently at higher resolutions) What s the Magic Number?

42 Corporate Ultra Conservative Corporate - Conservative

43 Corporate - SD Corporate Aggressive

44 Corporate Summary Bottom Line You should know the bits/pixel for each video that you produce If too low quality suffers If too high, may not stream smoothly and bandwidth costs (if a factor) may be unnecessarily high

45 Bottom Line You should know the bits/pixel for each video that you produce If too low quality suffers If too high, may not stream smoothly and bandwidth costs (if a factor) may be unnecessarily high Questions on Bits Per Pixel Should be 10:35 Download presentation handouts At

46 Introduction to Adaptive Streaming What it is How the various alternatives work RTMP (server-based) HTTP (no server) ID existing technologies Transmuxing What is Adaptive Streaming? One stream in, multiple streams out Streams switched transparently to adapt to factors like: Changing delivery bandwidths (avoid hard stops) CPU utilization at client (avoid frame drops)

47 Key Benefits Match stream quality to connection and playback platform used by viewer Mobile Desktop OTT Technology Overview Two types of systems Server-based (Flash, RTMP) HTTP HTTP Live Streaming (HLS) Smooth Streaming HTTP-based Dynamic Streaming (HDS) Dynamic Adaptive Streaming over HTTP (DASH)

48 RTMP Flash - Overview 1. Uses standard MP4/F4V files as encoded (no chunking) 2. Persistent connection between player and server 3. Player monitors: - Buffer - CPU utilization 4. Requests different stream when needed 5. Server sends different stream Issues with RTMP Server required: May increase cost (because servers cost $$) May limit scalability (if not enough servers for all viewers) RTMP packets can get blocked by Firewalls RTMP packets do not take advantage of HTTP caching mechanisms Less efficient for popular videos Some CDNs are dropping support for RTMP

49 In Contrast, HTTP Technologies Don t require a streaming server Better scalability Lower cost Ubiquitous CDN support Use HTTP protocol so: No firewall issues Will leverage standard HTTP caching structures More efficient for popular videos Bottom Line RTMP-based Dynamic Streaming has been most popular technology Market is moving towards HTTP

50 Apple HTTP Live Streaming (HLS) Encoder creates: Chunked video files Index file (M3U8) Sends to HTTP Server Player Retrieves index Monitors buffer Changes streams as necessary The Manifest File Structure

51 Perspective All HTTP Technologies work the same way Create chunked data files (or segments within longer file) Create index files (also called manifest) Placed on HTTP server Player side Monitors playback buffer and (sometimes) CPU use Changes streams as necessary Uses index files to find the right files Adobe HTTP Dynamic Streaming (HDS) MP4 Into Packager.F4F.F4M Media file chunks Manifest files that tell player where to find file chunks Player driven system Player monitors heuristics Retrieves different stream as necessary

52 Smooth Streaming How It Works Manifest file (.ism) Chunked content file (ismv) Dynamic Adaptive Streaming over HTTP (DASH) Like all HTTP-based technologies, it has Fragmented video chunks (or single file with segments) Manifest files Supports multiple codecs, container formats and manifest file formats

53 Where is DASH? Lots of smoke, but no real fire No native support on any platform Plug-ins available on most platforms Microsoft/Google working on browser support Where is DASH? DASH committee working on H.264-only subspec that Adobe/MS will endorse Apple/Google (Android) have not announced support Royalty picture not cleared DASH for computers/mobile is very much a work in process Likely will find native support in OTT platforms first (because closed system), but HLS is very entrenched

54 DASH Alternative? HLS Several pre-fab video players (JW Player) are adding HLS support (As you ll see) this makes HLS available on computers, mobile and OTT If these become pervasive, HLS could become the dominant format over DASH Transmuxing Technologies Perspective: most producers serve multiple clients Desktop - Flash (or Silverlight or DASH) AND Mobile - HLS for ios/android (maybe) OTT - HLS In the past, that meant two separate encoding and delivery workflows Separate encoder for each target Now, multiple streaming that: Input one set of streams, and Transmux to create second set for different target

55 Transmuxing Technologies Options Technology providers - Wowza, Real, Microsoft, Adobe Transmuxing Not re-encoding re-wrapping file into a different container format Creating necessary manifest files Delivering files to HTTP server All in real time

56 Perspective Key point: If serving multiple targets, you must produce using lowest common denominator H.264 encoding parameters Must be all baseline for streams targeted for mobile If so, can use one set of files to deliver to all three groups Bottom line: If serving multiple targets, must consider transmuxing Questions on ABR? Should be 11:10 Download presentation handouts at

57 Choosing a Delivery Technology Two Scenarios Single video file, no DRM, live or captioning HTML5 with Flash fallback should work for browser-based playback and OTT If you need adaptive, live, DRM or captions, choosing a path is much more challenging Distributing Single Files Desktop Flash/HTML5/ Mobile 100% playback of HTML5/H.264 OTT Each service has own delivery structure, typically MP4 files are recommended

58 When Producing for Flash Flash Player Video codec Profiles Audio codec Container formats Playback Specifications H.264 ONLY, not MPEG-4 Baseline, Main, High AAC, AAC-LC, HE-AAC MP4 (preferred), F4V, M4V, M4A, MOV, 3GP Understanding the HTML5 Playback Environment HTML5 introduction HTML5 penetration - desktop HTML5 codec support

59 HTML5 Overview HTML5 s key benefit Death to plug-ins everywhere (Particularly Flash) How it works Instead of obtaining decoders for H.264 and other codecs in plug-ins Browsers supply players and decoders Use <Video> tag in HTML to call player HTML5 Operation For video tag to work: 1. Browser must be HTML5 compatible 2. Browser must supply appropriate decoder Two key markets Desktop Mobile

60 Penetration of HTML5-compatible Browsers on Desktops Not HTML5 Comp+ So, at best, HTML5 is 69% of the market on desktops HTML5 Codec Support H.264 Camp IE, Safari, Chrome Google announced plans to remove H.264 1/2011, hasn t yet WebM camp Native Firefox, Chrome, Opera Via plug-ins IE 9/Safari

61 HTML5 and H.264 Flash Player Video codec Profiles Audio codec Container formats Playback Specifications H.264 ONLY, not MPEG-4 Baseline, Main, High AAC, AAC-LC, HE-AAC, HE-AACv2 MP4 (otherwise, may call a different player) Desktop Analysis HTML5 can access 69% of desktops (maximum) To access, you must produce two file versions H.264 Chrome, Safari, IE9 Chrome leaving? In 1/2011, Google said Chrome would drop H.264; it hasn t yet Firefox coming? Mozilla adding support for Android Firefox 17, so H.264 may be coming to Firefox soon (at least of OSs with H.264 support, which doesn t include Windows XP) Web M Firefox post 3.6, Opera post 10.6, Chrome

62 Distributing to Mobile HTML5-100% support in ios, Android, Windows 8 phones and tablets H % support, though, as seen, profiles and levels differ Distributing to OTT Channel schema varies by device (HTML5 isn t relevant) All devices play H.264 video up to (at least) 1080p, High Profile Any video configured for mobile/computers should play on OTT

63 Optimal Single File Strategy HTML5 with Flash Fallback HTML5 to all mobile devices HTML5 to all computers running HTML5 compatible browsers Fallback to Flash for non-html5 compatible browsers Can encode WebM & H.264 for optimal support Encode H.264 only and have Mozilla/Opera play Flash What is Flash Fallback? Video tag MP4 WebM If all else fails, play Flash From Sorenson Squeeze 9

64 Scenario 2 When you need: Adaptive streaming Live streaming DRM Closed captioning Targeting Desktops Requirements may extend beyond just video DRM, captions (public) Multicast/P2P (intranets)

65 Bottom Line? Flash or HLS Use JW Player in website So long as Flash is installed, will play HLS streams One set of streams for desktop, ios, OTT Targeting Mobile * * Android has issues playing back HLS - bit.ly/rayburn_android

66 Realistically? It s Just Not Easy ios HLS Android Universal coverage AIR application HLS 56% penetration and aspect ratio issues Windows Phone 8 Smooth Targeting OTT Flash is non-existent HLS is ubiquitous and generally the preferred technology Can implement smooth in most platforms if preferred

67 Adobe Primetime Library that sits above Flash Player Adds HLS (this summer) DASH (end of year) Includes SDKs for ios/android ios SDK will not include DASH Android SDK includes HLS stack that avoids HLS playback issues on that platform OTT support for both DASH/HLS by end of year Even with Primetime (licensing fees apply), DASH will not be available on all platforms Summary HLS is the only technology available on every target platform Today, DASH is not available on any platform Even though DASH is technically superior to HLS, it s hampered by: The lack of player support The potential for royalties Seeming lack of interest from Apple and Google (for Android, not Chrome)

68 Choosing a Delivery Technology Should be 11:35 Download presentation handouts at Producing Adaptive Streams Basic configuration options Number of streams Resolutions/data rates H.264 parameters Encoding adaptive streams Key frame settings Bitrate control Audio settings

69 The Big Question One set of streams for all devices? Customize streams for each class What We Know Most producers customize Turner Broadcasting NBA League Pass

70 My Consulting Experience Big sites tend to customize Large network in the US Separate streams for web, mobile, OTT Movie site in US Ditto, though some crossover Smaller sites Tend to use one set of files; all baseline Why the Same Set of Streams? Simplifies encoding (encode fewer streams) Can transmux Create one set for Mobile Transmux to Flash/OTT

71 Synthesis There is no right or wrong way I recommend: Attempt to find one set of streams that satisfies all using Baseline profile Test to see if Main or High delivers noticeably higher quality If so, customize for different targets If not, go with one set of streams Mobile First Slowest connection, lowest quality Configure for best service to mobile Try to configure at same resolutions as low end computer targets Apple Copyright Tech 2013 Jan Ozer, Note All Rights Reserved TN2

72 Desktop (browser-based) Next At least one stream for each window size in web site (HBO) Try to use same configuration as mobile Then High End Mobile, Desktop and OTT Full screen viewing on all devices Highest quality streams that you can afford Apple Tech Note TN2224

73 Stream Count Bottom Line At least one stream for each playback window More streams required for HD than SD SD usually 3, 4 maximum HD up to 11 More for entertainment than education/business Entertainment about the experience Business it s about making sure the viewer can watch the stream More for subscription than general entertainment Provide more options when viewer is paying What Resolution? Never encode at larger than source Scaling upwards degrades quality Resolution should match playback window whenever possible Optimal quality and playback efficiency If you can t match playback window, it s better to scale up to larger resolutions than to scale down to smaller More efficient playback (GPU assisted) More efficient bandwidth consumption

74 What Data Rates? Considerations Must be sufficiently far apart to: Avoid constant switching Make a meaningful quality difference Will vary with stream size Smaller gaps at lower bandwidths Larger gaps at higher bandwidths What Data Rates? MTV Schema

75 How do encoding parameters change? Now we know stream count, resolution and data rate How do we customize encoding for adaptive? Key frame settings Bit rate control Audio parameters Key Frame Interval Why important - RTMP Flash stream switches occur at key frame Key frame location must be identical in all streams Use same interval Disable scene change detection Typically shorter (2-5 seconds) to enable more responsive switching

76 Key Frame Interval Why important HTTP technologies - key frame must be first frame of every chunk Key frame interval must divide evenly into chunk duration If 9-sec. chunks, use key frame interval of 3 sec As with RTMP, key frame location must be identical in all streams, so: Use same interval Disable scene change detection VBR vs. CBR Most conservative - CBR Or constrained VBR Max data rate % of target

77 In General - Audio Parameters Most conservative-same parameters for all files Popping can occur if audio parameters change But, does t optimize experience at higher bit rates In General - Audio Parameters If you do switch audio parameters Switch from stereo to mono at same per channel sampling rate and bit rate From 64 kbps/44 khz/16-bit/mono To 128 kbps/44 khz/16-bit/stereo Test to ensure no artifacts when switching streams

78 RTMP Flash Sources Abhinav Kapoor, Live dynamic streaming with Flash Media Server 3.5, (adobe.ly/kapoorlivefms) Maxim Levkov, Video encoding and transcoding recommendations for HTTP Dynamic Streaming on the Flash Platform, (adobe.ly/levkovhttp) Larry Bouthillier, How to do Dynamic Streaming with Flash Media Server, website (bit.ly/fmsdynamic) Tutorial: On-demand HTTP Dynamic Streaming, Adobe website (bit.ly/ondemanddynamic) Encoding Guidelines Dynamic Streaming for Flash over HTTP, Akamai website (bit.ly/akamaiwhitepaper). HTTP Flash Resources Best sources: Maxim Levkov - Adobe - very detailed recommendations adobe.ly/levkovhttp Akamai - White paper: Encoding Guidelines for Dynamic Streaming for Flash over HTTP bit.ly/akamaiwhitepaper

79 Configuring your ABR streams Questions? Should be 11:55 Download presentation handouts at