PDF《Encoding for HTML5》

2011 Jan Ozer, All Rights Reserved Producing for HTML5 ? All browsers have their own players, no specifications (that I could find) ? Baseline, Main, High all supported up to 1080p ? Ditto for AAC-LC, HE-AAC, HE-AAC v2 ? Use MP4 file since F4V or MOV could trigger Flash or QuickTime players

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2011 Jan Ozer, All Rights Reserved Profiles and Levels ? General Rule - use highest supported profile and level on target ? When producing H.264 for HTML5 deployment, this means High profile, any level ? When producing for multiple platforms, like HTML5 and iOS, have to use lowest common denominator format Copyright ?

2011 Jan Ozer, All Rights Reserved Original iPod (to- 5g) iPod nano/ classic iPod touch/ iPhone iPhone

4 /iPod touch

4 iPad

1 iPhone 4S iPad

2 Device spec Screen resolution 320x240 320x240 480x320 960x640 1024x768 960x640 1024x768 Aspect ratio 4:3 4:3 16:9-ish 16:9-ish 4:3 16:9-ish 4:3 Codec spec Video codec H.264 H.264 H.264 H.264 H.264 H.264 H.264 Max video data rate

768 kbps 2.5 Mbps 2.5 Mbps

14 Mbps

14 Mbps

50 Mbps

50 Mbps Max video resolution 320x240 640x480 640x480 720p 720p 1080p 1080p Frame rate

30 fps

30 fps

30 fps

30 fps

30 fps

30 fps

30 fps Profile/level Baseline to Level 1.3 Baseline to Level 3.0 Baseline to Level 3.0 Main to Level 3.1 Main to Level 3.1 High to Level 4.1 High to Level 4.1 Audio codec AAC-LC AAC-LC AAC-LC AAC-LC AAC-LC AAC-LC AAC-LC Max audio data rate

160 kbps

160 kbps

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

48 kHz, stereo

48 kHz, stereo Encoding for iDevices ? 1080p playback unproven: use 720p ? These are maximum settings;

not recommended

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2011 Jan Ozer, All Rights Reserved Entropy Encoding ? Two options: ? CABAC (Context-adaptive binary arithmetic coding) ? More efficient (e.g. better quality), but harder to decode ? CAVLC (Context-adaptive variable-length coding) ? Less efficient, easier to decode ? General rule: ? Use CABAC when available (Main, High profiles) Copyright ?

2011 Jan Ozer, All Rights Reserved What Would YouTube Do? ? High Profile ? CABAC

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2011 Jan Ozer, All Rights Reserved What are I, B and P Frames? ? B - looks forward and backward to previous I and P frames (Bi-directional interpolated) ? No frames refer to B-Frame (most of the time) ? I-Frame - encoded without reference to other frames (also called Key Frames) ? P - looks backward to I and P frames (predictive) Copyright ?

2011 Jan Ozer, All Rights Reserved What do I Need to Know About Key Frames? ? Enable

1 key frame every ten seconds or so ? Helps playback interactivity ? Enable key frames on scene changes ? Optimizes quality

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2011 Jan Ozer, All Rights Reserved What do I Need to Know About B Frames? ? Use B-frames when available ? Main and High profiles ? Use an Interval of

3 (number of B frames between I and P-Frames;

(IBBBPBBBPBBBPBBBP) ? Reference frames (both P and B- frames) ? Number of frames searched for redundancies ? Use

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2011 Jan Ozer, All Rights Reserved Apple Compressor - Compression Settings ? Available options and presentation varies by encoding tool ? Apple'

s is very simple ? Can set key frames ? Frame Reordering enables B-frames;

can'

t control interval Compression Type: Choose codec here

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2011 Jan Ozer, All Rights Reserved AME - Compression Settings Profile/Level: ? Adobe lets you choose Profile and level directly ? No Entropy Encoding controls ? No controls over B-frame ? Can set key frame interval Copyright ?