Muxes, Codecs, Transcoders

[zehd]

Hi all. My eyes are literally falling out onto the desk as I type this - I've done so much reading. OK, not literally, but... :-)

Anyway, I'm finally taking a real look at DTV as there are three decent ATSC OTA channels in my area. I'm using my Haup HVR-1600 card for this.

I should also say that I'm trying all this with GB-PVR 1.4.7. So far I don't think I've come across anything that is really app specific, so I'll stick with the 'opponent' I know..

I'm kind of disappointed that the wiki doesn't have a more straightforward walkthough. I suppose I might try to tie it all together as soon as I understand it better... (the codecs page is missing some stuff!)

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In the analog days, I knew that I could have a fairly weak Recording Server, record a show (with the hardware encoder PVR150)... even if that same machine couldn't playback the show..

I'm pretty sure I've fallen into the same boat here. My server can record a TS file, though it really doesn't like playing back the file...

I'm pretty sure that the TS file is OK, as it will play on a faster machine..I've also tried the cyberlink mux and output to MPG.

Well, here are my questions...

The digital files are huge, specifically in dimensions (1920x1080).. either as TS or MPG output. Is there a mux, where one can set the output dimensions. I suspect that that would require more grunt from the server.. the stream is probably 1920x1080 and so if there's no downsizing, then less work... But is there a real time solution?

Asking people about codecs, is like asking them which team to cheer for, or which gas station has better gasoline (petrol)... But it seems my system is having trouble viewing the large TS (or MPG) files, whenever I use the usual codecs (like available in SAF)

So aside from getting a faster machine, what would be some ideas to get more grunt...? I've done quite a bit of tweaking already

And finally, post processing: I am AGAIN looking at post processing the TS file, to get a smaller MediaMVP friendly file...

I'm able to transcode either a TS or a muxed MPG at about 17fps with either Mencoder or ffmpeg... That's slow...

Of course, I really should be thinking of demuxing the file (which involves me learning about what I just said) so I wonder if anyone knows of a fast commandline tool that will make my large files small.

Thanks...

[sub]

The digital files are huge, specifically in dimensions (1920x1080).. either as TS or MPG output. Is there a mux, where one can set the output dimensions. I suspect that that would require more grunt from the server.. the stream is probably 1920x1080 and so if there's no downsizing, then less work... But is there a real time solution?

When doing digital recordings, the size of the recording on disk pretty much comes down to the bitrate used by the broadcasters. The mux filters, which produce the .ts or .mpg file that is written to disk, wont really make any significant difference to this. They always write the same MPEG data to disk, but vary a little in the container file that is wrapped around it. None will downsize it for you.

Pretty much your only option is PostProcessing to convert the recording to another format. As you've discovered, this can be pretty hard on machines, since it needs to decode and then encode the video in the stream. Your CPU can do this at 17 fps with your current software. There is no magic solution short of faster CPUs etc. If you're lucky, you might find a utility that can use modern video card GPUs for assisting with the encoding, but I've not looked into this myself.

[mvallevand]

Of course, I really should be thinking of demuxing the file (which involves me learning about what I just said) so I wonder if anyone knows of a fast commandline tool that will make my large files small.Thanks...

I think you might want to consider saving the bother and buying 1 or 2 TB of storage. They are only $60 and $90 these days.

Martin

[zehd]

I think you might want to consider saving the bother and buying 1 or 2 TB of storage. They are only $60 and $90 these days.

Martin

It's not a disk space that's the problem... I think it's my CPU/video card that's causing me the trouble of playback...

And as sub pointed out, I could just post process everything, which would be painfully slow (for me).. because a processed file plays fine.

And of course I want the smaller mpgs (dvd format) so they will play properly on the Media MVP... though.. I seems to have read somewhere that you got the mediaMVP to play TS files...

[zehd]

hmmm... the ts file will play back fine with mplayer...(on any computer I throw it at) that tells me that I have a codec problem, dammit... :-(

I have played with my codecs... and as many on the board has posted... it ain't easy wrangling them... I'll bet GB-PVR just has to jump through too many hoops (for playback)

[mvallevand]

Sorry I thought size with the problem for the host generally mpeg2 HD is pretty easy on the PC. I assumed that since the OTA HD stations in Calgary are available in SD, you didn't really need to waste the effort transcoding at this point.

Note that with mvpmc and NPVR even with SD you still won't get a North American ts files to play on the MVP because of AC3 audio.

Martin

[pBS]

yep, ac3 is a problem for mvp..and hd sizes also...would have to resize hd ..
what cpu do you have? what video card?
mostly it comes down to can the video hardware do it? then do you have good driver version? as saf ffdshow should work fine, as well as some cyberlinks..
cpu shouldn't be an issue unless your card can't do hardware deinterlacing...

i use ffmpeg .5 to demux and to mux, and also to re-encode files pretty fast...[near realtime on hd, mpeg2]
worst thing about re-encoding hd is you have to use diff settings for 1080i and 720p...
tried mencoder also but ffmpeg files still look better...
for speed with encoders, use highish bitrate and no quality tweaks..even with -sameq ffmpeg shrinks atsc by more than half... [from 14000 to around 6000]
i use this for hd stuff..

Code:

"ffmpeg.exe" -ss 2 -y -i %1  -async 200 -qscale 4 -s 720x480 -vcodec mpeg2video -ac 2 -acodec mp2 -ar 48000 -ab 160k "%~dpn1.mpg"

and depending on input material, get 30-50fps..
you might try http://code.google.com/p/ffmbc/ [broadcast ffmpeg]

[zehd]

Thanks guys... So I ended up working up my new version of ZProcess to work as a soild queue-able Post Process so that I can get a MVP Friendly MPG

Since downsizing a 1920x1080 AC3 file to anything playable for the MVP is almost the same, and for me, entirely not RealTime for on the fly transcoding (Greater than 30fps), I set up a profile where the TS is converted to a 720x480 file, Stereo MP2, and vbitrate at about 4800k. THis gives me a transcode fps at around 20-22 fps.

File size changes from 4.3 GB for a 30 minute show to about 850MB.... I then Comskip the MPG, replace it in the video folder, and mod the database to point to the new file... and voila..

If I set the profile to 352x240, then I get about 28-31 fps.. and GB-PVR/MVP tries to view the on the fly file... but it doesn't last long.. There's just not enough overhead...

@ Martin... Yeah, I could get SD OTA channels, but the point of the excerise is to work with the digital... and High Def stuff looks great!

@ Paul, I'm gonna play with ffmpeg some more.. But I have been primarily using MEncoder as I'm also able to to do colour/brightness tweaks. It will be interesting to see if I can get real time on the fly transcoding...

And as far as playing the native TS files straight on my underpowered system... well... of course I'm in codec hell, even though I thought I'm at a minimum... but the Transcoded files look pretty decent, have comskip, and nary a skip...

[zehd]

yep, ac3 is a problem for mvp..and hd sizes also...would have to resize hd ..
what cpu do you have? what video card?
mostly it comes down to can the video hardware do it? then do you have good driver version? as saf ffdshow should work fine, as well as some cyberlinks..
cpu shouldn't be an issue unless your card can't do hardware deinterlacing...

i use ffmpeg .5 to demux and to mux, and also to re-encode files pretty fast...[near realtime on hd, mpeg2]
worst thing about re-encoding hd is you have to use diff settings for 1080i and 720p...
tried mencoder also but ffmpeg files still look better...
for speed with encoders, use highish bitrate and no quality tweaks..even with -sameq ffmpeg shrinks atsc by more than half... [from 14000 to around 6000]
i use this for hd stuff..

Code:

"ffmpeg.exe" -ss 2 -y -i %1  -async 200 -qscale 4 -s 720x480 -vcodec mpeg2video -ac 2 -acodec mp2 -ar 48000 -ab 160k "%~dpn1.mpg"

and depending on input material, get 30-50fps..
you might try http://code.google.com/p/ffmbc/ [broadcast ffmpeg]

So I tried out ffmpeg .5 and even .6.1 and tried your command line and also played around.. running right from a batch file or shelled out from ZProcess... any which way I sliced it, MEncoder and ffmpeg were comparable at around 25-30 when dimensions where -s 352x240... But then that didn't lok all that good enough for the effort...

I fear it's coming down to simple CPU grunt... and it'll be a while before I grunt up...

But it's forcing me to be ingenious.. like distributed server processing :-)... I am getting all my content processed quick enough... and comskip on 'high'def is really making my ex jealous. She's using a Cable Co DVR and totally hates having to shuttle through commercials... heh heh heh...

[pBS]

yea, i suspect it is cpu holding you back...but that's true for any realtime encoding..
i was getting very workable times on a c2duo 2.5ghz...and there's other tweaks to speed it up some..maybe 5-10fps better..but pq will suffer for some tweaks..