Reverse AVI using DirectShow

[harish.kasi...@gmail.com]

Hello everyone,

My goal is reverse an AVI file so that I can play backwards. After
reading the archives the following is the solution I came up with.

1) Extract the all the images in bitmap format from the AVI file.
2) Use the PushSource Filter sample from the SDK to create a new AVI
file. I guess I will also have to generate proper time-stamps.

I would like to know if this is correct or is there a better way to
deal with it.

Thanks in advance.
Regards,
Harish

[Thore Karlsen [MVP DX]]

That should work fine. You could extract one frame at a time by playing
the graph backwards, stepping back one frame at a time.

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[Thore Karlsen [MVP DX]]

On Thu, 15 Sep 2005 14:30:43 -0500, Thore Karlsen [MVP DX]
<s...@6581.com> wrote:

>>My goal is reverse an AVI file so that I can play backwards. After
>>reading the archives the following is the solution I came up with.
>>
>>1) Extract the all the images in bitmap format from the AVI file.
>>2) Use the PushSource Filter sample from the SDK to create a new AVI
>>file. I guess I will also have to generate proper time-stamps.
>>
>>I would like to know if this is correct or is there a better way to
>>deal with it.

>That should work fine. You could extract one frame at a time by playing
>the graph backwards, stepping back one frame at a time.

.. and by stepping back I mean seeking, of course. Have the graph
paused, and seek back to the previous frame. Extract it, tell the
PushSource derived filter about the new frame, and repeat.

[Iain]

If you have the disk space, I'd be inclined to extract all the bitmaps into
a directory, numbered 0 to n and then read them back in in reverse order.

I'm thinking that, if your AVI is compressed, you may have issues with
frame seeking.

Iain
--
Iain Downs (DirectShow MVP)
Commercial Software Therapist
www.idcl.co.uk

[Thore Karlsen [MVP DX]]

On Thu, 15 Sep 2005 22:57:41 +0100, Iain <Ia...@idclTAKEAWAY.co.uk>
wrote:

>>>>My goal is reverse an AVI file so that I can play backwards. After
>>>>reading the archives the following is the solution I came up with.
>>>>
>>>>1) Extract the all the images in bitmap format from the AVI file.
>>>>2) Use the PushSource Filter sample from the SDK to create a new AVI
>>>>file. I guess I will also have to generate proper time-stamps.
>>>>
>>>>I would like to know if this is correct or is there a better way to
>>>>deal with it.

>>>That should work fine. You could extract one frame at a time by playing
>>>the graph backwards, stepping back one frame at a time.

>> .. and by stepping back I mean seeking, of course. Have the graph
>> paused, and seek back to the previous frame. Extract it, tell the
>> PushSource derived filter about the new frame, and repeat.

>If you have the disk space, I'd be inclined to extract all the bitmaps into
>a directory, numbered 0 to n and then read them back in in reverse order.
>
>I'm thinking that, if your AVI is compressed, you may have issues with
>frame seeking.

Yes, if the video is compressed using temporal compression, it would be
a tradeoff of disk space vs. speed. Raw video frames are awfully large,
which is why I would be inclined to do one frame at a time.

[Iain]

On Thu, 15 Sep 2005 17:02:33 -0500, Thore Karlsen [MVP DX] wrote:

> Yes, if the video is compressed using temporal compression, it would be
> a tradeoff of disk space vs. speed. Raw video frames are awfully large,
> which is why I would be inclined to do one frame at a time.

Clearly, I am a fan of brute force and ignorance! You have to cow these
Damned Computers somehow...

[Thore Karlsen [MVP DX]]

On Fri, 16 Sep 2005 09:54:16 +0100, Iain <Ia...@idclTAKEAWAY.co.uk>
wrote:

>> Yes, if the video is compressed using temporal compression, it would be
>> a tradeoff of disk space vs. speed. Raw video frames are awfully large,
>> which is why I would be inclined to do one frame at a time.

>Clearly, I am a fan of brute force and ignorance! You have to cow these
>Damned Computers somehow...

In my case I have a lot more free CPU cycles than I have free space on
my hard drive. :)

[harish.kasi...@gmail.com]

Thanks for the replies. It has given me the confidence to go ahead.

Let me check if AVI file has a temporal compression. I will update once
I have some concrete results.

Thanks,
Harish

[harish.kasi...@gmail.com]

Thanks for all the inputs. Just to confirm for others, the method
described above works fine. I was able to create a Reverse AVI file.

Point to note is that the AVI file did not have any temporal
compression.