datamosh: all I frames in video: how to get p frames?

[botzi]

hello,

i'm trying to learn how to datamosh for a school project. i've found all the tutorial on how to do it but have run into a problem. my video do not have any p frames and have way to many i frames before and after compression. in order to datamosh my videos need p frames. i'm using virtualdub on a pc as was recommended by all the datamosh tuts out there. i follow all the instructions and everything seems to go right until i get to the part where you have do delete some i frames. i'm using premeire to convert my .mov and .mp4 files into .avi. could that be the reason?

any help would be greatly appreciated. i'm 100% noob at video stuff. have to do this for a class.

thanks!

[Hoser Rob]

Some people who are much more expert than I am may have a better answer than me, but my first impulse would be to convert the file ... you wouldn't have to change format or codec necessarily ... and increase the distance between keyframes.

[jagabo]

Go to the export codec settings in VirtualDub, set the GOP size, and disable b-frames (assuming you only what I and P frames).

[botzi]

Some people who are much more expert than I am may have a better answer than me, but my first impulse would be to convert the file ... you wouldn't have to change format or codec necessarily ... and increase the distance between keyframes.

Yes, that's what I think the tutorials are trying to get you you to do. There are 2 main PC tutorials on the web and all other posting refer back to those. One of them just uses Avidemux to delete the I frame from your second clip. The other first uses VirtualDub with the FFDSHOW codec to make I frames appear every 500 frames or so. I've followed the tutorials to the T. Everything looks the same and is appears to be working until I get to the point where you're supposed to delete "one of the I frames". The problem is that I have hundreds of them on all my videos. I've tried video from the web, my camera, processed with Premiere and not processed with Premiere.

Thanks for helping!

[botzi]

Go to the export codec settings in VirtualDub, set the GOP size, and disable b-frames (assuming you only what I and P frames).

I scoured through VirtualDub but could not find the "export codec settings". I did notice that Avidemux has those settings however. The Datamosh tutorials do have you change the GOP and disable b-frames in Avidemux and then compress and save. For some reason unbeknownst to me it doesn't affect my video. They all still have a bunch of I frames and no P frames.

Could it be that I started with MP4s that I captured from Youtube which i then converted to AVI using Premiere?

Thank you for helping.

[jagabo]

I scoured through VirtualDub but could not find the "export codec settings".

Video -> Compression... select a codec, press Configure. Note that some codecs are I frame only (MJPEG for example).

[poisondeathray]

I scoured through VirtualDub but could not find the "export codec settings"

in vdub, video=>compression

Could it be that I started with MP4s that I captured from Youtube which i then converted to AVI using Premiere?

Not if you re-encode it with P-frames (ie. take either the MP4 or AVI, then re-encode it in vdub with P-frames and a long GOP interval, the default for xvid is 250)

[botzi]

in vdub, video=>compression

Not if you re-encode it with P-frames (ie. take either the MP4 or AVI, then re-encode it in vdub with P-frames and a long GOP interval, the default for xvid is 250)

The Datamosh tutorials recommend FFDSHOW but I've looked through the configure settings and do not see any GOP settings in it. There is something called Quantization which mentions I frames. I've tinkered with these settings a little but to no avail.
Do you recommend that I used xvid?

thnx!

[botzi]

I scoured through VirtualDub but could not find the "export codec settings".

Video -> Compression... select a codec, press Configure. Note that some codecs are I frame only (MJPEG for example).

Thanks for pointing this out. I will stay away from MPJEG. So far I've usef .MP4 clips that i downloaded from Youtube but then I took them into Premiere and exported them as .AVI.

thnx!

[jagabo]

in vdub, video=>compression

Not if you re-encode it with P-frames (ie. take either the MP4 or AVI, then re-encode it in vdub with P-frames and a long GOP interval, the default for xvid is 250)

The Datamosh tutorials recommend FFDSHOW but I've looked through the configure settings and do not see any GOP settings in it.

It's called Keyframe Distance in ffdshow's FFV1 encoder settings. The other codecs in current builds of ffdshow (MJPEG, Huffyuv, DV, uncompressed ) are all I frame only.

[poisondeathray]

It really doesn't matter what you use (you're not tying to preserve the quality, you're trying to wreck it with "psychadelic" effects)

But if you are using a fairly recent ffdshow version, you should be aware they have dropped almost all the ENcoders . They dropped all the long GOP encoders (except FFV1, which is lossless but can use Long GOP). Huffyuv, uncompressed, DV are all I-frame only. So it won't work for you unless you use an old ffdshow build .

So yes, something like xvid will be easier to configure and use


EDIT: looks like jagabo beat me

[botzi]

It really doesn't matter what you use (you're not tying to preserve the quality, you're trying to wreck it with "psychadelic" effects)

But if you are using a fairly recent ffdshow version, you should be aware they have dropped almost all the ENcoders . They dropped all the long GOP encoders (except FFV1, which is lossless but can use Long GOP). Huffyuv, uncompressed, DV are all I-frame only. So it won't work for you unless you use an old ffdshow build .

So yes, something like xvid will be easier to configure and use


EDIT: looks like jagabo beat me

Okay I installed the Xvid codex and rebooted the all programs. In VirtualDub I go to video compress and choose Xvid and then configure. I do not see any setting though for GOP in Xvid either.

I'm going to try an old version of ffdshow.

Thank you!

[poisondeathray]

Okay I installed the Xvid codex and rebooted the all programs. In VirtualDub I go to video compress and choose Xvid and then configure. I do not see any setting though for GOP in Xvid either.

I'm going to try an old version of ffdshow.

Thank you!

There is a "more" button under quality presets . Push that and you will get another page of options. Maximum I-frame interval is the max GOP size

You can see this guide on page 3 for screenshots
http://www.divx-digest.com/articles/xvid_setup_page3.html

If you wanted only I and P frames (no B-frames), you could set max consec b-vop's to zero for example. If you don't care, just leave it default 2


Or if you wanted to go with ffdshow, old ffdshow builds are hosted here
https://www.videohelp.com/tools/ffdshow/old-versions#download

[botzi]

Success!! What finally worked for me was to download an old version of FFDSHOW. I'm embarrased to say that it took me 15+ hours to datamosh successfully even with the tutorials. In case you find yourself in a similar situation, your trying to datamosh with a PC.. make sure to download old versions of VirtualDub and FFDSHOW (provided that you are following the Youtube tuts).

Thanks jagabo, poisondeathray, Hoser Rob, for helping to solve this. Inventively I just went through a crash course on codex. Wow its a complicated thing!! At least now I better understand what datamosh is.

Happy Holidays!

[decobah]

Hi botzi,

I am also tryng to datamosh and have just stumbled across this post. I am having the same kind of problems you had and have tried a few older versions of ffdshow and VirtualDub but still can't get it to work.

Can I ask you what versions of ffdshow and VirtualDub worked for you?

Many thanks

[decobah]

It's ok! I think I've cracked it!!!!!

Using latest VirtualDub v1.9.11 and fddshow rev 3556.

Works a treat!



Thanks for posting the above information though. Was very helpful.