On2 VP6 FLV padding and other mod16 container related issues

[Umamio]

In Encodes to .flv using vp6vfw.dll version 6.4.2.0 with ffmpeg or mencoder (http://forum.doom9.org/showthread.php?p=1260442#post1260442), the resultant file is padded on playback at the bottom and stretched to the right till it reaches the next mod16 resolution.

i.e
File encoded at 322 x 178 would have an extra 14 pixels of padding to the bottom and 14 to the right to display at 336 x 192. The bottom padding consists of the bottom-most pixels repeated, but to the right the video appears to just be stretched slightly rather than padded.

http://tyrannosauruslex.dreamhosters.com/BotPad.jpg

Using mencoder I also have additional issue of some resolutions resulting in tilted distorted video that do not seem to occur using the ffmpeg method:

http://tyrannosauruslex.dreamhosters.com/Foobar&Pad.jpg

I have tested playback with FFplay and Mplayer and "Adobe Media Player" and through ffdshow and the On2 VP6 decoder.

However, when I encode to .avi using On2VP6, the padding is not present on playback using the On2 VP6 decoder, but is still present in ffdshow, mplayer, ffplay and others. Strangely, the padding appears at the top in this case, and the On2VP6 encoder does not seem to require a flip as it usually does.

http://tyrannosauruslex.dreamhosters.com/toppadding.jpg

I am not sure what this means exactly about when/how the padding is being applied but if anyone has any ideas, I would be very grateful to hear them.

This occurs with all different filetypes, whether or not I serve them through Avisynth (Avisource / Directshow/ ffmpegsource / dgdecode)

(the images are from the same video encoded at different resolutions, which is why the differently sized images)

[Selur]

Got a question or just stating what's happening to you?
(if you letterbox to stay mod 16 and make sure you don't break colorspace during filtering the distortions shouldn't happen)

[Umamio]

I was interested if anyone knew of a method to correct this particular behaviour with non-mod16 resolutions as some the specifications stipulated by the platforms requesting the encoded videos are strict, and often not mod16. Sometimes odd numbers, even(!)

If it was up to me, I would be encoding h264+aac to .flv, but I am wondering how some of the commercial On2VP6-capable encoding packages manage to produce these resolutions.

If I manage to get a version of the flv with identical codec settings from a commercial encoder is there some way I can compare the two files to at least determine where the differences are? Is there some way of analysing the header / structure of the flv?