HLS

Это для ipad-a. А сводная таблица выглядит так:



The following audio and video formats are supported:

Video: H.264 Baseline Profile Level 3.0 (iPhone/iPod Touch), Main Profile Level 3.1 (iPad 1,2)
Audio: HE-AAC or AAC-LC up to 48 kHz, stereo audio OR
MP3 (MPEG-1 Audio Layer 3) 8 kHz to 48 kHz, stereo audio

Note: iPhone 3G supports H.264 Baseline Profile Level 3.1. If your app runs on older iPhones, however, you should use H.264 Baseline Profile 3.0 for compatibility.

IPhone
1) H.264 video, up to 1.5 Mbps, 640 by 480 pixels, 30 fps, Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;

2) H.264 video, up to 768 Kbps, 320 by 240 pixels, 30 fps, Baseline Profile up to Level 1.3 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;

3) MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 fps Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats

IPhone 3G & 3GS
1) same
2) H.264 video, up to 2.5 Mbps, 640x480 pixels, 30 fps, Baseline Profile up to Level 3.0 with audio same as above;
3)same

IPhone 4G

1) H.264 video up to 720p (1280×720), 30fps, Main Profile level 3.1 with audio same as above;
3) same
4) Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 fps, audio in ulaw, PCM stereo audio in .avi file format

IPhone 4GS

1) H.264 video up to 1080p (1920×1080), 30 fps, High Profile level 4.1 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats;

Here are some important points to consider when creating your own Variant Playlists
Choosing the initial variant to be played

• • The first entry in the Variant Playlist will be played at the initiation of a stream and is used as part of a test to determine which stream is most appropriate. The order of the other streams is irrelevant.
    We recommend you point to a 150k stream for the cellular Variant Playlist.
    We recommend you point to a 240k or 440k stream for the Wi-Fi Variant Playlist.
    Where possible, encode enough variants to provide the best quality stream across a wide range of connection speeds
  • For example, encode variants at 150 kbps, 350 kbps, 550 kbps, 900 kbps, 1500 kbps.
  • When possible, use relative path names in Variant Playlists and in the individual .m3u8 Playlist files
  • Audio/Video Stream Considerations
    The audio streams should be exactly the same.
    Video aspect ratio must be exactly the same, but can be different dimensions.
    We recommend 400 x 224 for 16:9 content and 400 x 300 for 4:3 content

    
    

    А вообще говорят, экранов всего два — 320х480 и 768х1024 точек. Все остальное — просто картинки в 2x размере.

    
    

    Ссылка на блог, где рассказывается про Ref Frames.