Are there ways of circumventing constrained parameters bitstreams for SIF class applications and decoders ?
A. Yes, some. Remember that CPB limits pictures by macroblock count (or pixels/frame). 416 x 240 x 24 Hz sampling rates are still within these constraints. Deviating from 352 samples/line could throw off many decoder implementations which possess limited horizontal sample rate conversion abilities. Some decoders do in fact include a few rate conversion modes, with a filter usually implemented via binary taps (shifts and adds). Likewise, the target sample rates are usually limited or ratios (e.g. 640, 540, 480 pixels/line, etc.). Future MPEG decoders will likely include on-chip arbitrary sample rate converters, perhaps capable of operating in the vertical direction (although there is little need of this in applications using standard TV monitors where line count is constant, with the possible exception of windowing in cable box graphical user interfaces). Also, many CD videos are letterboxed at the 16:9 aspect ratio. The actual coded and display sampling dimensions are 384 x 216 (note 3
A. Yes, some. Remember that CPB limits pictures by macroblock count. 416 x 240 x 24 Hz sampling rates are still within the constraints, but this would only be of benefit in NTSC (240 lines/field) displays. Deviating from 352 samples/line could throw off many decoder implementations which possess limited horizontal sample rate conversion abilities. Some decoders do in fact include a few rate conversion modes, with a filter usually implemented via binary taps (shifts and adds). Likewise, the target sample rates are usually limited or ratios (e.g. 640, 540, 480 pixels/line, etc.). Future MPEG decoders will likely include on-chip arbitrary sample rate converters, perhaps capable of operating in the vertical direction (although there is little need of this in applications using standard TV monitors, with the possible exception of windowing in cable box graphical user interfaces).
