Forking the subject.... Den 03. mars 2015 10:10, skrev Mohammed Raad: > At MPEG we use this to determine the codec performance for the "random > access" case. I don't know why the 1 second interval was chosen and > don't think that its relevant in many use cases, but MPEG codecs are > aimed at satisfying a broad range of applications and so this test case > has been maintained. Members of the potential IETF activity may find > that this is an irrelevant test case.
The reasons for having non-initial I-frames that I know of: - To allow seeking in stored media. To jump to a specific point, you locate the last I-frame before the point you want to go to and run the decoder from that point to the point where you really want to go. With DASH being a prevalent mode of delivering stored media, and each DASH chunk starting with an I-frame, 5 seconds would be realistic for this. - To allow recovery from a known good state in streaming media. For interactive two-way media, you can explicitly ask for an I-frame and have the headend produce it; for other media, such as broadcast (the original use case for half-second intervals, as mentioned above), more complex schemes are needed (I've heard of technologies for storing a reference frame in some other form and transferring it out of band so that the decoder can initialize its state and start decoding without an I-frame, but I don't know if these are used in practice.) _______________________________________________ video-codec mailing list [email protected] https://www.ietf.org/mailman/listinfo/video-codec
