Aspect Ratio & Resolution Changing when Transcoding

[keertib]

I apologize if this question has been answered already, but I couldn't find an answer to it, so here it goes...

I'm running GB-PVR on my P4, Hauppauge pvr-150MCE, Radeon 9700Pro computer connected to a Sony 27" CRT TV (4:3 aspect ratio). I'm starting to experiment with transcoding my TV recordings to AVI (Dixv or Xvid) to save them. The problem I'm having is that the resolution/aspect ratio changes when I do this.

According to Windows Media Player, my MPEGs are 640x480, but the AVI files come out at as 720x480. When I play these AVI files on my laptop, they do indeed look streched. I'm wondering is this supposed to happen? Do I need to mess with settings for ffmpeg to get this correct?

Thank you very much!

[sub]

Cant say I've noticed it myself, but I've not spent too much looking closely at this.

Do I need to mess with settings for ffmpeg to get this correct?

Yeah, you may need to. Sorry!

[zehd]

I apologize if this question has been answered already, but I couldn't find an answer to it, so here it goes...

I'm running GB-PVR on my P4, Hauppauge pvr-150MCE, Radeon 9700Pro computer connected to a Sony 27" CRT TV (4:3 aspect ratio). I'm starting to experiment with transcoding my TV recordings to AVI (Dixv or Xvid) to save them. The problem I'm having is that the resolution/aspect ratio changes when I do this.

According to Windows Media Player, my MPEGs are 640x480, but the AVI files come out at as 720x480. When I play these AVI files on my laptop, they do indeed look streched. I'm wondering is this supposed to happen? Do I need to mess with settings for ffmpeg to get this correct?

Thank you very much!

If the MPEGs were recorded with your PVR150 then they are really 720x480, WMP does lie a lot...

What I suggest is transcoding 720x480 to 640x480 with the 4x3 flag set.. It looks like this. But don't take this example literally. It's copied from a test recording...

Code:

"C:\Program Files\devnz\gbpvr\Third Party\FFmpeg\ffmpeg.exe" -y -i "C:\TV\Recorded\Greys Anatomy\Greys Anatomy_20070315_22002301.mpg" [B]-deinterlace[/B]  -b 1250k -vcodec mpeg4 -ab 224 -ar 48000 -acodec mp3 -ac 2 -r 29.97 [B]-s 640x480[/B] -padtop 0 -padbottom 0 -f avi -vtag XVID [B]-aspect 4:3[/B]  "C:\TV\Override\Greys Anatomy_20070315_22002301.avi"

I've hilighted the pointers. You may also want to de-interlace...


Incidentally, ZProcess is quite helpful with Transcoding. It doesn't just do MVP...

[keertib]

Wow, thank you very much for the quick replies sub and zehd!!

Thank you zehd for the example code as well, I'll give that a try.

If the MPEGs were recorded with your PVR150 then they are really 720x480, WMP does lie a lot...

I think I've read in some other post that NTSC is 720x480, so this would make sense. However, I copied the mpg file off the dvr computer to my external HD, and even my Mac says the mpg is 640x480. Any clues as to why this would be? Is this what GB-PVR captures because I set my aspect ratio to 4:3 in the config?

Again, thanks a lot!

[sub]

It should be recording 720x480.

[zehd]

Wow, thank you very much for the quick replies sub and zehd!!

Thank you zehd for the example code as well, I'll give that a try.


I think I've read in some other post that NTSC is 720x480, so this would make sense. However, I copied the mpg file off the dvr computer to my external HD, and even my Mac says the mpg is 640x480. Any clues as to why this would be? Is this what GB-PVR captures because I set my aspect ratio to 4:3 in the config?

Again, thanks a lot!

Well it doesn't matter. The nice thing about FFmpeg is that it doesn't really care about the input dimensions. So I'll bet using the info I gave from before, will still help, as it makes sure the aspect ratio will be 4x3

[gEd]

I have setup 4:3 and 16:9 versions of the xvid profile as freeview (DVB) shows can sometimes be broadcast with different aspect ratios. Only problem is I have to preview mpg first to find out what the AR is. It would be nice if this could be automated....

[Cahill84]

I'm noticing that a show is being broadcasted as 2.35:1 aspect ratio, but right now I have my capture resolution set to 720 x 480 (under the capture device tab in the config). I would think that it would be increasing the file size, because it's recording extra information. The real problem though is that I cannot get it to display full screen in GBPVR. I've tried altering the settings of the aspect ratio stuff, but it hasn't worked- citation: http://gbpvr.com/pmwiki/pmwiki.php/Tips/AspectRatios.

1) I am ultimately looking to transcode these items using divx, and I was curious if I should just implement the ffmpeg transcode into my batchfile and simply remove so many pixels from top and bottom to force the changed ratio to 2.35:1.
2) Should I change the capture resolution to get it to view full-screen? Or is there some feature in config.xml that I haven't altered as of yet that I should?

[sub]

I'm noticing that a show is being broadcasted as 2.35:1 aspect ratio, but right now I have my capture resolution set to 720 x 480 (under the capture device tab in the config).

2) Should I change the capture resolution to get it to view full-screen? Or is there some feature in config.xml that I haven't altered as of yet that I should?

These resolution settings only apply to analog cards, and analog cards only ever produce 4:3 video. So if you're recording this on the analog side of your HVR-1600, then the broadcaster is probably transmitting it in letter box mode (ie 720x480, but with big bit of this set to black at the bottom and the top). BTW, because of this hardcoding to 4:3 done on analog cards, the auto aspect ratio doesnt work well - BDA devices fare much better.

1) I am ultimately looking to transcode these items using divx, and I was curious if I should just implement the ffmpeg transcode into my batchfile and simply remove so many pixels from top and bottom to force the changed ratio to 2.35:1.

I'm fairly sure ffmpeg does have command line parameters that can be used to do this. I'm guessing you're not often going to dealling with 2.35:1 video, so I'd probably just manually run ffmpeg to do this, rather than trying to make some automated scheme.

[zehd]

To double up on subs comments, it sounds like the program was broadcast in letterbox, and they sent out black bars on top and bottom. GB-PVR just got and recorded a 4x3 image....

I don't know the exact command lines, but yeah, you just slice off the top and bottom using a crop command, probably in the same command that will transcode it to AVI. That way you're getting it all in one action...

If I remember correctly, Stattik has a script that either can do it for you, or point you in the correct direction to create the commandline...