ATI HD 650 Analog mpg size questions

[luttrell1962]

I'm not sure what part of the forum to post this hardware might be more appropriate.

I analyzed my mpg files that get recorded they are 720x480, my output from my cable box is just standard analog. Is this coming from my card like this in mpg2 format? The files are huge for a NTSC signal. I'm working on conversion down to 480x270 keeping the aspect ratio and changing bit rate to vbr.

1. I have question I always have some black on the left and right sides. Not as much when viewing a 16x9 video, but a lot in pillerbox. Does anybody know how many pixels I can strip off the sides during the ffmpeg conversion. I can trial and error it but that will take forever.

2. I've added the following code to config.xml, I want avi file but gb-pvr is passing an mpg extension to the destination file. This caused me problems until I figured it out. Now I copy the file in the gb-pvr directory and use it for conversion since you can't have the same input and output files. ffmpeg croaks.

Code:

<Conversion name="Divx 2-passanalog" exe="Divx2passanalog.bat" cmd="{SOURCE_FILE} {DEST_FILE}" targetExtension=".avi" />

[JonnyCam]

How huge are we talking about?

You can change the bitrate for your analog signal (in the capture source, you can adjust what the medium quality is - used for all quick recordings)

[luttrell1962]

3-4 gigs for a hour file on medium settings. Probably set bitrate to 1000 and still have decent quality I will try that.

[Sykor]

3-4 gigs for a hour file on medium settings. Probably set bitrate to 1000 and still have decent quality I will try that.

A 90mins movie can take up 6/7 gigs in a commercial DVD (depending on the bitrate used), so 3/4 gigs per hour is what is to be expected from dvd standart mpeg2 in medium quality. You can tweak your bitrate settings to lower to space needed.

I believe you're comparing the analog mpeg2 output, with a pure digital feed capture, right? Digital broadcast have a very low bitrate, and you can't get that sort quality/bitrate ratio with a regular consumer product (I believe), hence the extra space used when trying to get similar quality through analog signal.

I generally set my recordings to use the low quality in VBR, and I get around 2Gb per hour with an decent/watchable quality, although noticeably worse that a digital feed.

You can try 1000 bitrate, but I'd expect miserable results with it. Speaking from my experience with both the (Hauppauge) PVR-USB2 and the PVR-500, using 3500 VBR (my low bitrate settings). I get borderline results: I can watch it, but I wouldn't brag about them.

[luttrell1962]

All blocky looking. But if I run the file through ffmpeg @ 1500k cbr it looks pretty much like the original go figure. It converts fast on my machine about 350-400fps.

Here's the batch file I am using, I crop off the top because some of cable channels have weird flashing on the top.

Code:

xcopy %1 temp.mpg
"D:\Program Files (x86)\Devnz\GBPVR\Third Party\ffmpeg\ffmpeg.exe" -y -i temp.mpg -ab 128k -acodec libmp3lame -ac 2 -ar 44100 -b 1500k -deinterlace -threads 8 -croptop 16 -vtag divx %2
del temp.mpg
DEL ffmpeg*.log
rem IF EXIST "%~dp1%~n1." DEL %1
EXIT

[JonnyCam]

But if I run the file through ffmpeg @ 1500k cbr

Best option here is buy a new harddrive and worry about encoding at another time (or never)

discs are cheap these days, and if you record the signal at rubbish quality, you won't be able to upsample it make it too much better.

In saying that, I think divx is a more efficient codec, so that might explain why it looks like the original (when you say original, you mean the analog feed, or the original mpeg recording?)

[pBS]

ya gotta remember that the hardware encoder doesn't have the ability to analyze previous frames or future frames to make it look better...it has to encode as it comes..
so ffmpeg or any other compressor will always look better and get better bitrates..
[but it can't do it on the fly]
any mpeg4 variant will look better at same bitrate..just a more advanced codec...
h.264 looks best of all, but takes most time to encode...
it's all about finding your preferred middle ground...

so record at decently high bitrates[5k-9k], then compress later to xvid,etc. for storage..
and use vbr for a bit extra quality and possibly smaller files.....

[luttrell1962]

I have a 1000g's to play with, but it will fill up in weak at standard file sizes. A dvd will only hold one or two shows.

With a multicore fast machine might as well put the cores to work and compress down the files.

The ATI hd 650 card has a 3d comb filter and enhances the resolution every other scan line somehow. When I run ffmpeg without the -deinterlace option playback looks funny the in-between scan line shimmer. I read on another post that a different codec will fix this. I do lose some quality with the -deinterlace option.

[pBS]

yea, sounds like the playback codec...i use ffdshow for divx/xvid,etc...
ffmpeg deinterlacing seems to just half the resolution[bob] instead of really deinterlacing [adaptive]..

you should leave interlacing as it was recorded,[interlaced, or not] so playback can take care of it..

i use mencoder for avi output instead of ffmpeg..

Code:

mencoder.exe -noskip -ovc lavc -oac lavc  -lavcopts vcodec=mpeg4:vqscale=8:acodec=libmp3lame:abitrate=128  -ffourcc XVID -o "%~dpn1-2.avi" %1

[pBS]

oh yea, need to add "-flags +ildct" for ffmpeg to do interlaced material...
or if using built-in ffmpeg, use just -ildct..

it's ok to always have there as it doesn't affect non-interlaced material..
then everything will look good with ffmpeg..

a good line to use with built-in ffmpeg is:

ffmpeg.exe -y -i %1 -f avi -ab 224k -ac 2 -acodec mp3 -ildct -vcodec mpeg4 -qscale 8 -vtag XVID "%~dpn1.avi"

other versions require different syntax for same options..