Converting DV to 3GP --> Output Looks Rather Blocky & "Pixelate

[SnakeGirl]

Hello, it's me again w/another question about ffmpegX. i was doing more test conversions, this time from a .dv file to .3gp. After the conversion process was completed, i played the .3gp output file & found that the picture was rather "pixelated"--sort of blocky looking, w/somewhat large size squares rather than the finer resolution i would hope for & which was on the source .dv file--i'm not sure if that is the right terminology, but i don't know how else to describe it. Are there parameters or settings in ffmpegX that i can tweak or adjust to get better picture resolution in the output? Thanx again.

[fugu]

Welcome to 3gp, isn't it grand? Seriously though, 3gp is very low bitrate indeed, the compromise that will give the biggest bang for the buck increase in quality is to reduce the frame rate on the output. 15 or even 12fps, on a cell phone size screen it will look ok. I'm not sure what verizon uses for vcast tv but I do believe they output 30fps but at a higher bitrate. If your target device can handle h264 then give that a shot at the same sizes, it might be ok. Hope this of some help.

[Case]

1/ Set the Video Size to the native resolution of of your viewing device (phone?). If yours support 320x240, then change that from the default 176x144.
2/ The default bitrate is quite low to get small files. Use the Best button in the bitrate calculator to get an optimized (higher) bitrate.
3/ In the Options tab, you could tweak the quantizer setting, which relates to quality range to use. Lower values mean better quality. Set Qmax to a lower value to improve the quality. Setting both Qmin and Qmax to 2 would encode about as good as it can get. Setting a Qmax anywhere between 2 and 24 will give some in-between quality.

• More quality will result in larger files. Even fancy mobiles have a maximum memory storage.
• The effective bitrate should stay below the maximum of your mobile, or the file will not play (well).

Some samples:
a. Default bitrate of 30 kbps; Qmin=2, Qmax=24; output filesize norm at 100%.

b. 'Best' bitrate set to 68 kbps; Qmin=2, Qmax=24; output filesize at 164%.

c. Qmin=2, Qmax=2; bitrate value ignored; output filesize at 476%.

[SnakeGirl]

Welcome to 3gp, isn't it grand? Seriously though, 3gp is very low bitrate indeed, the compromise that will give the biggest bang for the buck increase in quality is to reduce the frame rate on the output. 15 or even 12fps, on a cell phone size screen it will look ok. I'm not sure what verizon uses for vcast tv but I do believe they output 30fps but at a higher bitrate. If your target device can handle h264 then give that a shot at the same sizes, it might be ok. Hope this of some help.

Hi & thanx for the suggestions. Just FYI, my device is a Samsung SGH-T639 cell phone on T-Mobile. Not sure if it can handle h264, how might i find that out?

[SnakeGirl]

1/ Set the Video Size to the native resolution of of your viewing device (phone?). If yours support 320x240, then change that from the default 176x144.
2/ The default bitrate is quite low to get small files. Use the Best button in the bitrate calculator to get an optimized (higher) bitrate.
3/ In the Options tab, you could tweak the quantizer setting, which relates to quality range to use. Lower values mean better quality. Set Qmax to a lower value to improve the quality. Setting both Qmin and Qmax to 2 would encode about as good as it can get. Setting a Qmax anywhere between 2 and 24 will give some in-between quality.

• More quality will result in larger files. Even fancy mobiles have a maximum memory storage.
• The effective bitrate should stay below the maximum of your mobile, or the file will not play (well).

Ooh, thanx much for the input & info! i believe the phone's native resolution is 176x220. Don't think it supports 320x240, but how can i find out for sure? And how would i find out what the maximum bit rate of my mobile is? Fortunately, this phone takes a microSD card (up to 2GB). Hopefully this is big enough to allow some room for picture improvement.

[SnakeGirl]

• More quality will result in larger files. Even fancy mobiles have a maximum memory storage.

Oh, i forgot to ask--if i try for better picture quality, i know i will get larger files, but will the conversion also take noticeably longer when i'm getting larger output files (or not really)?

[Case]

I believe the phone's native resolution is 176x220. Don't think it supports 320x240, but how can i find out for sure? And how would i find out what the maximum bit rate of my mobile is?

If it is not in the included booklet, on the Samsung website, or on other googled SGH-T639 forums, then you'll have to try and find out -- experiment.
For testing purposes, it may be a good idea to take a short clip, to cut down on encoding time.
I expect 176x144 to be the maximum video size, but you could try and see what happens with 220x176 videos.

Fortunately, this phone takes a microSD card (up to 2GB). Hopefully this is big enough to allow some room for picture improvement.

2GB eh? No worries then.

If i try for better picture quality, i know i will get larger files, but will the conversion also take noticeably longer when i'm getting larger output files (or not really)?

Bitrate and quantizer values have very little effect on encoding time, but a larger frame size would increase encoding time noticeably.

[SnakeGirl]

I believe the phone's native resolution is 176x220. Don't think it supports 320x240, but how can i find out for sure? And how would i find out what the maximum bit rate of my mobile is?

If it is not in the included booklet, on the Samsung website, or on other googled SGH-T639 forums, then you'll have to try and find out -- experiment.
For testing purposes, it may be a good idea to take a short clip, to cut down on encoding time.
I expect 176x144 to be the maximum video size, but you could try and see what happens with 220x176 videos.

If i try for better picture quality, i know i will get larger files, but will the conversion also take noticeably longer when i'm getting larger output files (or not really)?

Bitrate and quantizer values have very little effect on encoding time, but a larger frame size would increase encoding time noticeably.

Hey ... thanx so much for the examples you provided, they were EXTREMELY helpful! So far i've run tests using the same parameter values as in your examples (using the "Best" bitrate value of 68, & then the Qmin=2, Qmax = 2) to give me an idea of the quality range in the output. Boy, the Qmin/Qmax=2 settings gave me really EXCELLENT results! The output file size was significantly bigger @ almost 60 MB for a 13-minute video, but i can totally deal w/that. It played back very well on the phone, so i think that's all the tests i need to run for now--don't think i need to try the other sizes like 220x176 or 320x240, i'm really happy w/the results i've already gotten thus far.

i do have a question about the Process Information though, i noticed there were a number of warning messages in it:

Encoding started on Mon Jan 21 00:40:06 PST 2008
FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
Mac OSX universal build for ffmpegX
libavutil version: 49.0.0
libavcodec version: 51.9.0
libavformat version: 50.4.0
Input #0, dv, from '/Users/Princess/Movies/Belly Dance/Elektra/Elektra (Miscellaneous).dv':
Duration: 00:13:27.1, start: 0.000000, bitrate: 28771 kb/s
Stream #0.0, 29.97 fps(r): Video: dvvideo, yuv411p, 720x480, 28771 kb/s
Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Output #0, 3gp, to '/Users/Princess/Movies/Belly Dance/Elektra/Elektra (Miscellaneous).dv.ff.4.3gp':
Stream #0.0, 12.00 fps(c): Video: h263, yuv420p, 176x144, q=2-2, 68 kb/s
Stream #0.1: Audio: amr_nb, 8000 Hz, mono, 12 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
.
.
(a whole bunch of the same warning msgs. repeating in here ...)
.
.
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
video:59683kB audio:1261kB global headers:0kB muxing overhead 0.389711%
bench: utime=289.047s
Encoding completed on Mon Jan 21 00:54:44 PST 2008

What do these warning msgs. mean & do i need to do anything to eliminate them? The output video appears to be fine as far as i can tell & is plenty good enough quality for playback on my phone.

[Case]

Boy, the Qmin/Qmax=2 settings gave me really EXCELLENT results! The output file size was significantly bigger @ almost 60 MB for a 13-minute video, but i can totally deal w/that.

You're welcome. I'm glad it worked out okay.

i do have a question about the Process Information though, i noticed there were a number of warning messages in it:
[h263 @ 0x45a630]warning, clipping 1 dct coefficients to -127..127
What do these warning msgs. mean & do i need to do anything to eliminate them?

dct coefficients are Discrete Cosine Transform Coefficients, which are used in lots of image and video compression algorithms. Apparently the encoder wants these coefficients for this H.263 video between the values -127 and 127. Values outside that range are clipped to the minimum and maximum. Each time it finds such an out-of-range number, it is entered in the log.
The log is telling what the encoder is doing. The warning is just telling that it couldn't handle some of the numbers it is dealing with, and is changing values in order to cope with them, in the best way it can do that. Nothing to worry about, nothing you can do about it either...