Why are digital videodisc formats strictly locked to one resolution and framerate? Assuming it’s otherwise encoded to specification, why can’t we have 1080p DVD-Video or 480p BDMV?

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This might be more of an ELI12 because I already have a pretty good functional understanding of video codecs and the restrictions of physical digital media (so I understand why you can’t encode a DVD in something other than MPEG-2, and that you can’t fit a 1080p feature film encoded in MPEG-2 on a DVD, for example). But I don’t get why a strict resolution is necessary if a stream otherwise conforms to codec and max bitrate restrictions. Are hardware decoders like those in dedicated players substantially cheaper if they only have to expect one or two types of incoming stream? Is it a brand image thing where movie studios and the DVD/BD licensors are trying to create a uniform experience to increase buy-in and retention?

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Anonymous 0 Comments

Resolution? Because you needed to output something a CRT TV of the time could display and DVD was basically at the maximum resolution already. Most TVs expected lines to match their country’s TV specs. In the case of the NTSC aligned regions it was 480 lines visible out of 525 total while in PAL land it was 576 lines visible out of 625 total.

CRTs used electron guns and the deflection coils needed time to have their voltage change so drastically so there was a vblank period that took up part of the frame, hence 480 and 576 lines rather than the full 525 or 625 lines.

Likewise, frame rate conversion usually had artifacts, was terrible, and wasn’t really possible with cheap hardware in 1997. Plus TVs didn’t really do well with changing frame rates if they were older and you couldn’t be assured that the TV would even be able to display what the DVD player output if it deviated from its country’s standard output format.

It would be possible to display a DVD at certain lower resolutions and some pirated stuff indeed did but what was the point? You wanted to fit a movie that was as high quality as possible and the space available let you do that, short of a four hour movie.

BD is pretty much similar. You get 100GB of data on a disc, players that are engineered to take 1080p, why bother shitting up your presentation for what is effectively shits and giggles?