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  1. #1
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    It's possible to play vedio reverse order.

    Commonly, The order of playing vedio is toward end. It's possible to play vedio toward start? If it can, How to implement? Thanks?

  2. #2
    Nokia Developer Moderator
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    Re: It's possible to play vedio reverse order.

    AFAIK normal video playing APIs are not implementing functionality of reverse playing videos.

  3. #3
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    Re: It's possible to play vedio reverse order.

    I guess it'd also be rather fairly resource intensive with a progressive video enoding format where each individual frame for the whole video is not stored, but full frames are only stored periodically, and then only changes to the frames for subsequent frames until the next full frame, etc.

    Playing it in reverse would require, I suppose (I'm not a video format expert of any kind) that the whole video is first read to memory, or constant scanning of the file to back up and the regenerate all the frames so that the can be shown in reverse. Expensive in terms of memory consumed, processor power requirements, and that way also impacting power consumption (battery).

  4. #4
    Nokia Developer Moderator
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    Re: It's possible to play vedio reverse order.

    I would not fear from CPU/battery load, since all the frames have to be calculated for "normal" playback too. Assuming that positioning in the stream is possible (and it is usually possible, since the players support "clicking" into the middle of a video), the theory is that you have to calculate everything between two I-frames (http://en.wikipedia.org/wiki/Video_c..._picture_types), and play them in reverse order. Then locate the previous I-frame and repeat. Since you will always want to keep at least two segments in the memory (I1-I2 decoding, I2-I3 playback), that may mean a lot of data.
    Practically it is something what the built-in codecs will unlikely do for you, so some open-source solution could help - unless you want to write it from scratch. Movino project has/had an FFMpeg port as I remember, however a recent thread (from 3-4 days ago) indicates some problem with the download site. SourceForge may still help with some other projects.

  5. #5
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    Re: It's possible to play vedio reverse order.

    It's 264/mp4 code type. Are there any APIs to decode each frame?

  6. #6
    Nokia Developer Moderator
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    Re: It's possible to play vedio reverse order.

    I suppose you could try experimenting with Dev Video APIs available in API Plug-in, though note the compatibility issues as well as that these APIs do not really have any public documentations.

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