ffmpeg help - 16:9 HD -> 4:3 SD

[Braklet]

I've noticed that when transcoding dvr-ms files to mpg, the sync really sucks.

DVR-MS -> MPG sync is always spot-on when I remux with VideoReDo.

ZProcess sure looks very cool, but I'm gonna see what I can do with the supplied ffmpeg.exe a while longer.

[Spartan]

Just subscribing to see how this turns out. I have a HVR-1600 and with the new TV season getting under way, I am going to have to use the ATSC tuner to record some shows. I have used ffmpeg to try and get them to a format that my MVP would play on, but the results have not been good. All sorts of vertical stripes in the resulting video. Audio seems to be ok, though.

As for recording, I've tried .ts .mpeg and dvr-ms source. Not really sure which is the best though.

Anyhow, I'm anxious to see what you all come up with!

[jksmurf]

Just curious: Does gui4ffmpeg work with HD-files?

I "think" it does. It certainly does Xvid/DivX and H264. I asked a few questions in that forum last Dec and the Author (a german fellow IIRC) kindly changed / updated the code for me. Perhaps he could do the same for you if it doesn't?

k.

[zehd]

When I first installed my ATSC tuner card, I tried the two muxes that were described as supporting direct-to-MPEG-wrapper. My results were atrocious, so I ran back to the safety of DVR-MS wrappers.

The proprietary M$ format hasn't been a problem for me since I use VideoReDo to edit out commercials and remux to native MPEG file format.

A friend of mine took one of my HD DVR-MS sample clips and said that the following command line created an almost-perfect 720x480 MPEG-2 file, except that it introduced an A/V sync problem:

ffmpeg -i sample.dvr-ms -b 4000000 -vcodec mpeg2video -s 720x480 -ab 128000 -r 29.97 sample.mpg

I told him that when I remuxed with VRD, it complained about some errored audio and video frames that it corrected. Perhaps these could be responsible for the sync problem?

For the time being, I plan to run with ffmpeg to see if I can make a small batch file to do the cropping and downsample. I figure it can't hurt to at least learn more about this powerful utility.

Thanks!

That a/v sync is what I was talking about. I played with delays, and it slipped out and got worse after a bit...

I'll bet that muxes will be the end to this journey. One you are able to save in MPEG format (and happy with it) then the ffmpeg cropping is a piece of cake...

[Braklet]

Re: "will ffmpeg work with HD files" the answer is yes. My testing samples were recorded from the US Fox network as 1280x720 (720p) 60fps as reported by ffmpeg and GSpot.

Note that the version of ffmpeg.exe delivered with GB-PVR v1.0.16 DOES NOT accept DVR-MS input! Later builds of ffmpeg.exe do. For that reason all my experimentation involved the following transformation BEFORE running ffmpeg:

Record HD as DVR-MS -> Remux to MPG file with VideoReDo.

VideoReDo solves many audio/video sync issues and I found no evidence of sync problems in my ffmpeg tests. If I can get a later build of ffmpeg to work with DVR-MS source and not introduce sync problems, I may be able to fully automate this process.

Anyway, this parameter list worked very well with the ffmpeg.exe delivered with GB-PVR. My video clip went from 16:9 to 4:3, retained very good quality after the 4Mbps downcode and audio went from AC3 to MP2 (stayed in sync):

ffmpeg -i "sample.mpg" -croptop 0 -cropbottom 0 -cropleft 166 -cropright 166 -aspect 4:3 -b 4000000 -vcodec mpeg2video -s 720x480 -r 29.97 -ab 256 sample2.mpg

I still plan to play around with this but welcome comments.

My sample is native HD and does not have pillarbars, so I have to tune my crop values to achieve my SD conversion goal.

[zehd]

Re: "will ffmpeg work with HD files" the answer is yes....

...If I can get a later build of ffmpeg to work with DVR-MS source and not introduce sync problems, I may be able to fully automate this process.

That is the issue isn't it? to fully automate the conversion from dvr-ms to a mvp ready MPEG.

There was never any question whether ffmpeg could transcode (down-code?) a large MPEG to a smaller one. Even the version that ships with GB-PVR can do that, and well...

The real question has always been, (and discussed a lot) is 'How do I convert and down-size transcode a Wide Screen dvr-ms to a mvp ready MPG automatically ?'

VideoRedo would not be an automatic solution. The answer was stated by sub several times, "Get the MUX working so that you save the recordings in native MPEG. Then auto-post-conversion/transcoding is a piece of cake.'

I know you like VideoRedo, but if you want 'automatic' then get the muxes working

[zehd]

OK...this is where I say I was wrong. :o

I have found several scripts that will work to commandline control videoredo.

That means that one might be able to automate the dvr-ms to mpg procedure...

I will look closer at it. It involves using a VBScript, that is called via a batch file. Sounds convoluted, but it's not. I had something like that with ZProcess Version 1 (Source code lost- have to start on that feature by scratch again...)

I would love to work on this and stream line the process. If you could make available a small 30-60 sec dvr-ms clip (ftp, web, email to my hotmail) I would get something out soon...

I'll make the solution portable, but I'll also build it into ZProcess, where it would also call ffmpeg or mencoder to do cropping...

Let me know if you're interested...

[Braklet]

That is the issue isn't it? to fully automate the conversion from dvr-ms to a mvp ready MPEG.

Actually, no. The issue in my case is "I'm stuck recording the HD ATSC channel, so how can I convert native SD material to my standard DVD archive format."

The AC3->MP2 is a nice benefit that will make viewing from my MVP a lot easier, too.

There was never any question whether ffmpeg could transcode (down-code?) a large MPEG to a smaller one.

Maybe not to you, but I have (had?) zero experience with ffmpeg and I have already seen a WIDE range of development with the 3 versions I've played with thus far. So rather than wait for you to add something automagic and convenient to ZProcess (which looks very nice, BTW), I'd rather learn something I can use myself.

I know you like VideoRedo, but if you want 'automatic' then get the muxes working

I already manually edit commercials. The automatic commercial skip simply can not match the single frame precision of a native MPEG editor. If I can compose a little batch file with the right ffmpeg command line, all I have to add is a single file drag-drop to the process.

Aren't the automatic methods geared towards ALL recordings? I neither want nor need to convert every recording. Only native SD material recorded off of an HD stream.

The only ATSC mux I might have any luck with is whatever shipped with my tuner card. In the 10 minutes I played with the AVerMedia software, I can't recall any sync problems. I believe the files were saved as MPG as well. The other linked muxes were flat out terrible on my system, and I wasn't inclined to dive down that hole. I'm pretty sure the AVer stuff was not DirectShow compliant, but I could take another look.

[Braklet]

I have found several scripts that will work to commandline control videoredo.

Oh really?... <wheels in head start spinning>

I would love to work on this and stream line the process. If you could make available a small 30-60 sec dvr-ms clip (ftp, web, email to my hotmail) I would get something out soon...

I'm interested in that. Give me a little bit of time and I can send a URI in a forum private message. Is that sufficient?

TIA!

[Braklet]

Sample available and waiting; URI sent via PM.

Thanks!