miniDV compressibility

[adoniscik]

Background
I am trying to encode my NTSC DV videos to xvid. I render to huffYUV (YUY2 mode) after editing as an intermediate step. My Avisynth script merely runs tomsmocomp to deinterlace the file. If the shoot took place indoors I use some form of noise reduction. I have a separate MPEG-2 encode for T.V. viewing, so I want the MPEG-4 encode for P.C. viewing to be deinterlaced.

The camcorder is a Panasonic PV-DV953. The xvid encoding options are: 2Mbps with two passes, qpel, gmc, default B-frame and quantizer options (but Soulhunters V5 matrix), VHS6, MSP6, VHQ1, chroma motion, turbo;-), chroma optimizer ... basically everything you need for a decent encode. The source is full frame.

Problem
Why do I have to go to bitrates as high as 2Mbps before I can get something barely acceptable? DVDs look great at half that bitrate.

My hypothesis is that camera shake is throwing off motion estimation. My work is hand held -- consider this is a constraint -- and I am using optical image stabilization as it is. Moreover, I suspect the camcorder is applying excess sharpening.

P.S. Is it better use huffYUV in RGB mode in this case?

[Video Dude]

Why do I have to go to bitrates as high as 2Mbps before I can get something barely acceptable? DVDs look great at half that bitrate.
2Mbps Xvid is not that high for high quality full frame DV. (NTSC DV is 720x480 @ 29.97fps and PAL DV is 720x576 @25fps).

Remember that DVDs are IVTC when encoded to XVID, so thats progressive 24fps. That is 20% less frames to encode then DV 29.97fps. DVDs are also letterboxed or widescreen so you really don't have to encode the full frame because most people clip them out when encoding.

For the Xvid encodes for the PC, instead of encoding at full frame 720x480 (I'm using NTSC for the example), you should resize to 640x480. This will adjust the aspect ratio to 4:3 and you will save some bits.

Also DV in general is known to require more bits when encoding.

[stephanV]

Originally posted by adoniscik
Why do I have to go to bitrates as high as 2Mbps before I can get something barely acceptable? DVDs look great at half that bitrate.
pictures, pictures, pictures...

i think a lot of people wont believe you when you say an MPEG2 encoding at half the bitrate looks better than MPEG4, with all other constants (frame rate, frame size, etc.) the same. It is said that on noisy sources XviD is not the best of the (MPEG4-)codecs, but i doubt it would make that much a difference, but who knows.. :)

doing a *very rough* estimate with bpp = 0.2 you would end up with a bitrate of 0.2*29.97*720*480 = 2072 kbps, so your not that far of actually.


My hypothesis is that camera shake is throwing off motion estimation. My work is hand held -- consider this is a constraint -- and I am using optical image stabilization as it is.
maybe you should look for a deshaker filter then...

[adoniscik]

I know it was not clearly worded. I meant DVDs converted to MPEG-4 vs. miniDV converted to MPEG-4.

Do deshakers automatically detect scene transitions, and pans? What other drawbacks do they bring?

[theReal]

I experienced the same with PAL DV - MPEG4 compressibility is horrible compared to DVD to MPEG4 compressibility.

One reason has already been mentioned: DVDs are usually letterboxed, not 4:3 fullscreen.
A second reason is that movie DVD sources are already filtered before encoded to MPEG2. Both the pre-processing and the MPEG 2-encoding make the video much more compressible for your MPEG4 codec. (I guess an uncompressed HD movie source would be most horrible to compress to MPEG4)

btw. using blend deinterlacing instead of interpolated deinterlacing increases DV compressibility (and mostly doesn't look worse - sometimes even better). I once did some test runs with tomsmocomp and Fielddeinterlace (Decomb) and as far as I can remember tomsmocomp was better (in terms of compressibility) than fielddeinterlace(blend=false) but fielddeinterlace(blend=true) compressed best.


Why do I have to go to bitrates as high as 2Mbps before I can get something barely acceptable? DVDs look great at half that bitrate. I don't believe that (must be a calculation error). The lowest you could use for a barely acceptable DVD would be something like 3-4 Mbps. However for DV source you shouldn't use anything lower than 6-7 MBps if you roughly want to keep the quality.

[adoniscik]

I don't believe that (must be a calculation error). The lowest you could use for a barely acceptable DVD would be something like 3-4 Mbps. However for DV source you shouldn't use anything lower than 6-7 MBps if you roughly want to keep the quality.
You probably mean MPEG-2; I meant MPEG-4. Why use MPEG-4 at 6MBps?

[theReal]

Ok, you meant "DVDs look great at half that bitrate (when compressed to MPEG4)"

Then you're absolutely right, of course! :)

What I understood was "DVDs (=MPEG2 Videos) look great at half that bitrate"