I have an app that delivers video content using HTTP Live Streaming. I want the app to retrieve the appropriate resolution based on the devices screen size (either 4x3 or 16x9). I ran Apple's tool to create the master .m3u8 playlist file (variantplaylistcreator) and got the following:
#EXTM3U
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=248842,BANDWIDTH=394849,CODECS="mp4a.40.2, avc1.4d4028",RESOLUTION=480x360
4x3/lo/prog_index.m3u8
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=384278,BANDWIDTH=926092,CODECS="mp4a.40.2, avc1.4d4028",RESOLUTION=480x360
4x3/mid/prog_index.m3u8
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=787643,BANDWIDTH=985991,CODECS="mp4a.40.2, avc1.42801e",RESOLUTION=480x360
4x3/hi/prog_index.m3u8
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=249335,BANDWIDTH=392133,CODECS="mp4a.40.2, avc1.4d4028",RESOLUTION=640x360
16x9/lo/prog_index.m3u8
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=384399,BANDWIDTH=950686,CODECS="mp4a.40.2, avc1.4d4028",RESOLUTION=640x360
16x9/mid/prog_index.m3u8
#EXT-X-STREAM-INF:AVERAGE-BANDWIDTH=780648,BANDWIDTH=987197,CODECS="mp4a.40.2, avc1.42801e",RESOLUTION=640x360
16x9/hi/prog_index.m3u8
This does cause my live stream to switch between video quality correctly, but it seems to randomly pick whether it uses a 4x3 or 16x9 resolution.
Is there a way to have it select the correct dimensions automatically, or do I need to have multiple playlist files and have a device request a specific one? For example, if on an iPad do I need to detect that it's screen has a 4x3 dimension and request a 4x3_playlist.m3u8 that only has the 480x360 resolution option?
Update 2017:
Keeping the same aspect-ratio is only a recommendation in the latest HLS authoring guide:
1.33. All video variants SHOULD have identical aspect ratios.
Original answer:
Audio/Video Stream Considerations:
Video aspect ratio must be exactly the same, but can be different dimensions.
Select a playlist based on the User-Agent instead.