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Reverse play a Video (.mpg,.mov,.swf) file.


prashantakerkar
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Reverse play a Video (.mpg,.mov,.swf) file.

The easiest would be to load video file to some video editing software, such as e.g. VirtualDub, which you can download from http://www.virtualdub.org/ and use e.g. this tutorial:

Tutorial shows that you can load video file, and export to image sequence. Then reverse order of files on disk and import image sequence back to program and compress to final video file.

Google for "how to reverse video in [XXX]" where XXX is your video editing software.

ps. .swf is not video file. It's ShockWave Flash file format.

 

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(Some) compression algorithms for video use previous frames to increase efficiency. That means the files as such cannot be played backwards.

As stated above, the files can be converted to play backwards.

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6 minutes ago, Bender said:

(Some) compression algorithms for video use previous frames to increase efficiency. That means the files as such cannot be played backwards.

Majority of video file formats to compress more efficiently utilize key frames and intermediate frames. Key frame contains entire compressed image. Intermediate frame contains relative data from the last key-frame or key-frame with applied changes (previous frame).

When difference between raw frames is too large, it's the more efficient to store key-frame (with the all image data), rather than relative data.

To play backward codec must find previous key-frame, and generate intermediate frames from it. Video file format can contain entire table of the all key-frames (usually at the end of file). Key-frames can have special unique codes to allow codec to find them manually in stream of data. i.e. file.seek(random_position ); file.read(buffer,len); search in buffer for codes..

https://en.wikipedia.org/wiki/Key_frame

"In video compression, a keyframe, also known as an "intra-frame", is a frame in which a complete image is stored in the data stream. In video compression, only changes that occur from one frame to the next are stored in the data stream, in order to greatly reduce the amount of information that must be stored. This technique capitalizes on the fact that most video sources (such as a typical movie) have only small changes in the image from one frame to the next. Whenever a drastic change to the image occurs, such as when switching from one camera shot to another, or at a scene change,[1] a keyframe must be created. The entire image for the frame must be output when the visual difference between the two frames is so great that representing the new image incrementally from the previous frame would require more data than recreating the whole image.

Because video compression only stores incremental changes between frames (except for keyframes), it is not possible to fast forward or rewind to any arbitrary spot in the video stream. That is because the data for a given frame only represents how that frame was different from the preceding one. For that reason, it is beneficial to include keyframes at arbitrary intervals while encoding video. For example, a keyframe may be output once for each 10 seconds of video, even though the video image does not change enough visually to warrant the automatic creation of the keyframe. That would allow seeking within the video stream at a minimum of 10-second intervals. The down side is that the resulting video stream will be larger in size because many keyframes are added when they are not necessary for the frame's visual representation. This drawback, however, does not produce significant compression loss when the bitrate is already set at a high value for better quality (as in the DVD MPEG-2 format)."

 

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17 minutes ago, prashantakerkar said:

What will be the method for .swf Shockwave flash file format where .fla are source input files for compilation (correct me if I am wrong)?

Try editing it in Macromedia Flash Editor, or Adobe Flash Professional CC or similar flash editor..

 

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On 8/1/2018 at 7:40 PM, prashantakerkar said:

 

Is it possible to reverse play a Video file?
 

Sure. All you will need is:

Your existing media player.

Your existing television set or display device.

A pair of very keen eyes.

A space vehicle capable of traveling faster than the speed of light.

Method:

Set the file playing on your screen and wait for the program to end. Now don't hang about; get into your craft. I would advise plotting a course directly away from your TV. Now by traveling faster than c, you will eventually pass the photons that left your display. Which means by looking out the rear porthole you'll be able to see the movie running backwards. Of course, the further away from Earth you go, the smaller the picture will become. That is where the pair of very keen eyes comes in.

Edited by Star Walls
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