FFmpegx encoding problems

[geek rock]

I've encoded an SVCD-compatible MPEG-2 file using FFMPEGX (on a 700 iBook), and there are several problems with the file..

a) there are black borders top and bottom that were not present on the original source (they appear below the VHS tracking lines)

b) on fast moving scenes the scenes look extremely distorted.

you can see both problems in the picture below. the top pic is the resulting encoded file, the bottom is my original iMovie DV file.

this was encoded using the default SVCD template in FFMPEGX.





any ideas?

-Mark
[/img]

[major]

a) there are black borders top and bottom that were not present on the original source (they appear below the VHS tracking lines)

This is meant for keeping the aspect ratio of SVCD sized material on a TV screen. Have you selected PAL or NTSC size according to source?

b) on fast moving scenes the scenes look extremely distorted.

Open your DV file in QT player, open the info panel and set "High quality" and "Single field". Then do Apple-S to save. Then encode again.

[geek rock]

i selected the NTSC SVCD mode, and the file is an NTSC one.

I'll try the single field/high quality thing.. thanks!

-Mark

[geek rock]

i just tried a re-encode, and the black borders are still present, top and bottom.. are they removable?

i did the same as before, using the NTSC SVCD quick preset. the movie is NTSC.

[major]

Which image size is your source material?

[geek rock]

standard iMovie size, 720 x 480.

[major]

When input file is .mov there is no way of turning off the black bars. They are added to preserve aspect ratio. If source ratio is already good, no bars are added. I just encoded a sample 4:3 clip to SVCD NTSC and there were no black bars added. I think I should need your file to check what happens. Can you upload a chunk of it to some ftp site or iDisk?

[behoovedgirl]

mark had actually been doing this project on my mac.. so i've made a tiny clip of his original file and uploaded it to my idisk for you to see.

it's like 3/4 of a second long, and still 3.5MB. hopefully it won't be too much trouble to download, and will be long enough for you to work with.

http://homepage.mac.com/triumphsarm/everclearclip.mov

thank you for helping us out with this, we really appreciate your time
[/url]

[major]

Try this:
- rename your movie with a ".dv" extension instead of ".mov"
- encode it (it will encode only the video)
- export the audio to WAV with Quicktime player and then convert it to mp2
- finally use the "Tools tab" to "Mux as" SVCD the video and audio streams.

[geek rock]

thanks very much major, i'll give it a go (or get behoovedgirl to )

maybe this is something that could be worked on for the next release of the software though.. the seperate audio/video muxing is a tiny inconvenience, if you see what i mean.

great program though!

-mark

[behoovedgirl]

ok i've done everything you said.. i set the quicktime movie to "high quality" and "single field" modes. i changed the file name to dv, and re-encoded it, extracted the audio, converted it to mp2, then muxed them together... and the black boxes are gone, but now i've got a different quality problem...



there's horizontal-only lines across the video whenever there's motion. it doesn't look *as* bad on the TV screen, but they're still noticeably there.

now i had to encode it at 2100 kbit/s and author it as an xsvcd, because that's what it needs to be set at in order to fit it onto 1 CD. otherwise, all the other settings were that of a standard SVCD.

any ideas what could be causing it? thanks again for all your help thus far

[bilestyle]

Looks like a classic case of interlacing artifacts, try selecting deinterlace in the SVCD/VCD tab.

[behoovedgirl]

i just tried re-encoding it with "deinterlace" checked, and it didnt make a difference.

i've also tried different combinations of "not interlaced" "field" and "frame", and toggling VBR in the SVCD options tab, and none of them helped.

this is so confusing, it didn't do this when i encoded straight from the .mov... only after i renamed it to a .dv file. does anyone have any other ideas what could be causing this? i'm absolutely clueless!

[pants]

if you are going straight from a .mov file, the best way i got to work for svcd was with mediapipe, cause i kept getting the interace artifacts you're getting.

file browser (add file)
qt decode
scale
mpeg2nec set your svcd stuff and you want to set to interlaced bottom field first(if it's dv footage, cause that's the field order for dv footage)


this worked great. i'm not at my home comp so i don't have the exact svcd settings but if you want them i'll post them later.

pants

[behoovedgirl]

wooo i think i got it sorted.

i figured out the problem was directly related to the fact that i was encoding from a DV file, cos i tried a few others and it did the same thing.

so i started over and exported the video out of imovie as a motion jpeg A, and set the proportion to 640 x 480. this created a quicktime movie (which doesnt have the interlacing/artifact problems that the DV files did), and it was exactly the right proportions to not make any black bars on the top and bottom or sides when i encoded it with ffmpegx.

thanks again for everyone's help!

[major]

Looks like a classic case of interlacing artifacts, try selecting deinterlace in the SVCD/VCD tab.

Not deinterlace in the SVCD/VCD tab, but deinterlace in the mpeg-1/4 tab.

This may seem strange, but when file ends in ".dv" ffmpeg is used to decode, so deinterlacing is handled in the mpeg-1/4 tab.

I'll improve interface in future versions.