The QuickTime API supported reverse play around 1993 or so, when I enjoyed using it for "back and forth" animated sprites, and playing music videos backwards to reveal the satanic messages with demonic backmasking.
Reverse / Backwards Moonwalk - Michael Jackson - Better Than The Original!!!
Here's the documentation and code I wrote when working at Kaleida Labs (a joint venture of Apple and IBM) on a ScriptX animation library that used QuickTime and other renderers, and depended on QuickTime's support for playing videos backwards, and single stepping forward and backwards of course:
ScriptX's QuickTime renderer would even play audio backwards and at whatever speed, too. ScriptX had excellent multimedia clock synchronization, and we would have considered it a terrible bug if ScriptX was not able to seamlessly and transparently synchronize video and audio with any arbitrary clock, time offset, and time scale, no matter what the speed and direction.
I'm sad that 31 years later, web browser video and audio players (not to mention VLC) don't support hierarchical clocks like ScriptX did for multimedia synchronization. (Each child clock can have a time offset and time scale relative to its parent, and everything's automatically kept in sync, from the simulation to the renderer.)
Here is Kaleida's (then Apple's) 1993 patent on "Synchronized clocks and media players", which has long since expired in 2013:
>Abstract:
A media player and the clock which controls it are integrated into a single object. This integration may be achieved by the construct of inheritance between objects in an object oriented programming environment. A software class for player objects is established which inherits from a software class for clock objects. In this way, a player "is a" clock. This integration provides improved synchronization among different media, and simplifies design of applications which employ player objects and clock objects. Each object is synchronized to a RootClock object which operates at the speed of the fastest media player in the system. The RootClock may be separated into "low" order and "high" order components and a compare register in order to reduce interrupt overhead.
>[...] QuickTime essentially allows a multimedia player to process timebased data. Since the data are time based, QuickTime provides for the description of "time" (called time basis) for the data as well as a definition of the context for evaluating that "time." In QuickTime, a movie's or media's time basis is called its "timebase."
>A timebase is essentially a vector that defines the direction and velocity of time for a movie or media. The context for a timebase is called its time coordinate system. Conceptually, a time coordinate system provides an axis for measuring time. The time coordinate system, like a geometrical axis, is divided into units of measurement by a measurement system, called a time scale.
[...]
DonHopkins on Dec 29, 2018 | parent | context | favorite | on: Steve Jobs hired a career juggler to teach program...
Oh, of course I wish Apple and IBM had made it free!
But it included Apple's "crown jewels", the QuickTime player source code, and they were't going to give that away in 1995. Apple were even trepidatious about IBM having access to that source code.
Besides having proprietary decoders, it could also do some things you can't even do well with the Flash player or html video component today: like smoothly playing videos and music backwards!
Ever since the music industry switched from vinyl to CD, listening to demonic backmasking in Devil Music like the Beatles and Led Zeppelin's promotion of Satanism became much less convenient. ScriptX solved that important problem elegantly with its synchronized clock system, but today's HTML video player still hasn't, alas.
>Kaleida Lab's ScriptX (a multimedia programing language kinda like Dylan with classes) had built-in support for hierarchal clocks within the container (in the sense of "window" not "vm") hierarchy. The same way every window or node has a 2D or 3D transformation matrix, each clock has a time scale and offset relative to its parent, so anything that consumes time (like a QuickTime player, or a simulation) runs at the scaled and offset time that it inherits through its parent container. And you can move and scale each container around in time as necessary, to pause movies or simulations.) You could even set the scale to a negative number, and it played QuickTime movies backwards! (That was pretty cool in 1995 -- try playing a movie backwards in the web browser today!)
Yeah, I remember het AVI porn in the early 1990s where time alternated between forward and backward, thus providing an infinite video in only a few frames. (Probably it would have been more realistic with a sinusoidal rather than triangle-wave temporal waveform.)
I think there's a lot of space for experimentation here, generating video as an arbitrary three-dimensional slice of a potentially higher-dimensional space — like how horse-race photo-finish cameras map one vertical spatial dimension and one temporal dimension into two spatial dimensions for the photo, or how Julia-set animations map two of the dimensions of the four-dimensional Julibrot onto screen space while mapping a smooth path through the other two dimensions onto time. I've gotten some stunning still images by taking even fixed horizontal or vertical slices through video, but you could also do things like delay one side of the picture more than the other, or foreshadow future action by curving part of the frame into a timelike angle through the source material. It might be difficult to record a source video with more than one temporal dimension with a camera, but you can certainly do it with ray-tracing or other rendering techniques.
Presumably if you want to play a video backward with a modern codec, you need to buffer up decoded P-frames in memory from at least the previous I-frame — much like iterating backwards over the lines in a file, except that each "character" is a megabyte or two of YUV pixels. Should be totally feasible on a modern cellphone, even for aggressive modern formats that only have I-frames every few seconds… but it would be nothing short of a miracle in 1995! I guess MPEG-2 didn't exist yet, so maybe MPEG-1 with N=18, M=2 was the worst case you'd need to handle at that point? That should only require a 10-P-and-I-frame buffer.
The whole point that Remi was making is that doing this for one format is probably easy. Doing this for all formats in a consistent manner with a consistent experience is not easy, verging on impossible. Other players only support a limited set of formats, so can do this easily. VLC supports everything, so therefore has to handle all the bizarre quirks that make this a very difficult task.
Reverse / Backwards Moonwalk - Michael Jackson - Better Than The Original!!!
https://www.youtube.com/watch?v=IT_Aq2FjJo0
Here's the documentation and code I wrote when working at Kaleida Labs (a joint venture of Apple and IBM) on a ScriptX animation library that used QuickTime and other renderers, and depended on QuickTime's support for playing videos backwards, and single stepping forward and backwards of course:
ScriptX Animation Library:
https://www.donhopkins.com/home/catalog/lang/scriptx/anim.ht...
ScriptX Animation Implementation Module:
https://donhopkins.com/home/archive/scriptx/animimp.sx
ScriptX's QuickTime renderer would even play audio backwards and at whatever speed, too. ScriptX had excellent multimedia clock synchronization, and we would have considered it a terrible bug if ScriptX was not able to seamlessly and transparently synchronize video and audio with any arbitrary clock, time offset, and time scale, no matter what the speed and direction.
https://en.wikipedia.org/wiki/ScriptX
I'm sad that 31 years later, web browser video and audio players (not to mention VLC) don't support hierarchical clocks like ScriptX did for multimedia synchronization. (Each child clock can have a time offset and time scale relative to its parent, and everything's automatically kept in sync, from the simulation to the renderer.)
Here is Kaleida's (then Apple's) 1993 patent on "Synchronized clocks and media players", which has long since expired in 2013:
https://patents.google.com/patent/US5452435A/en
>Abstract: A media player and the clock which controls it are integrated into a single object. This integration may be achieved by the construct of inheritance between objects in an object oriented programming environment. A software class for player objects is established which inherits from a software class for clock objects. In this way, a player "is a" clock. This integration provides improved synchronization among different media, and simplifies design of applications which employ player objects and clock objects. Each object is synchronized to a RootClock object which operates at the speed of the fastest media player in the system. The RootClock may be separated into "low" order and "high" order components and a compare register in order to reduce interrupt overhead.
>[...] QuickTime essentially allows a multimedia player to process timebased data. Since the data are time based, QuickTime provides for the description of "time" (called time basis) for the data as well as a definition of the context for evaluating that "time." In QuickTime, a movie's or media's time basis is called its "timebase."
>A timebase is essentially a vector that defines the direction and velocity of time for a movie or media. The context for a timebase is called its time coordinate system. Conceptually, a time coordinate system provides an axis for measuring time. The time coordinate system, like a geometrical axis, is divided into units of measurement by a measurement system, called a time scale. [...]
https://news.ycombinator.com/item?id=18781950
DonHopkins on Dec 29, 2018 | parent | context | favorite | on: Steve Jobs hired a career juggler to teach program...
Oh, of course I wish Apple and IBM had made it free! But it included Apple's "crown jewels", the QuickTime player source code, and they were't going to give that away in 1995. Apple were even trepidatious about IBM having access to that source code.
Besides having proprietary decoders, it could also do some things you can't even do well with the Flash player or html video component today: like smoothly playing videos and music backwards!
Ever since the music industry switched from vinyl to CD, listening to demonic backmasking in Devil Music like the Beatles and Led Zeppelin's promotion of Satanism became much less convenient. ScriptX solved that important problem elegantly with its synchronized clock system, but today's HTML video player still hasn't, alas.
https://en.wikipedia.org/wiki/Backmasking
https://www.youtube.com/watch?v=5BDh_j5qAJ4
Here's a description of ScriptX's clock system:
https://news.ycombinator.com/item?id=18350511
>Kaleida Lab's ScriptX (a multimedia programing language kinda like Dylan with classes) had built-in support for hierarchal clocks within the container (in the sense of "window" not "vm") hierarchy. The same way every window or node has a 2D or 3D transformation matrix, each clock has a time scale and offset relative to its parent, so anything that consumes time (like a QuickTime player, or a simulation) runs at the scaled and offset time that it inherits through its parent container. And you can move and scale each container around in time as necessary, to pause movies or simulations.) You could even set the scale to a negative number, and it played QuickTime movies backwards! (That was pretty cool in 1995 -- try playing a movie backwards in the web browser today!)
Is it possible to play HTML5 video in reverse?
https://stackoverflow.com/questions/5277293/is-it-possible-t...
Kinda, but it's not smooth enough to sing along while dancing backwards and worshiping Satan to:
https://codepen.io/adrianparr/pen/qmCek
kragen on Dec 29, 2018 [–]
Yeah, I remember het AVI porn in the early 1990s where time alternated between forward and backward, thus providing an infinite video in only a few frames. (Probably it would have been more realistic with a sinusoidal rather than triangle-wave temporal waveform.)
I think there's a lot of space for experimentation here, generating video as an arbitrary three-dimensional slice of a potentially higher-dimensional space — like how horse-race photo-finish cameras map one vertical spatial dimension and one temporal dimension into two spatial dimensions for the photo, or how Julia-set animations map two of the dimensions of the four-dimensional Julibrot onto screen space while mapping a smooth path through the other two dimensions onto time. I've gotten some stunning still images by taking even fixed horizontal or vertical slices through video, but you could also do things like delay one side of the picture more than the other, or foreshadow future action by curving part of the frame into a timelike angle through the source material. It might be difficult to record a source video with more than one temporal dimension with a camera, but you can certainly do it with ray-tracing or other rendering techniques.
Presumably if you want to play a video backward with a modern codec, you need to buffer up decoded P-frames in memory from at least the previous I-frame — much like iterating backwards over the lines in a file, except that each "character" is a megabyte or two of YUV pixels. Should be totally feasible on a modern cellphone, even for aggressive modern formats that only have I-frames every few seconds… but it would be nothing short of a miracle in 1995! I guess MPEG-2 didn't exist yet, so maybe MPEG-1 with N=18, M=2 was the worst case you'd need to handle at that point? That should only require a 10-P-and-I-frame buffer.