encoding ATSC at 1920x1080i 25fps

[duffbeer911]

hello ... i am looking for some advice for encoding mpeg-2 ATSC files at 1920x1080i 25fps .... i've read that originally ATSC did not support this format, but now it has been updated to.

The hardware players we are using (alcorn DVM-HD) support ATSC 1080i 25fps.

We purchased mainConcept Reference to encode these files but as far as I can see it will not let me encode ATSC in anything other than US standards. The closest I can get is doing a blu-ray HD encode, but the results aren't great through this player...

Does anyone have any suggestions on how I can create these encodes? if we need other software? What is the main difference between the ATSC mpeg2 and the blu-ray mpeg2?

any help or guidance is much appreciated . thanks

[Guest]

Yes, 1080i 25fps is a supported ATSC format.

One option is to use the HCEnc MPEG2 encoder (free) to create your video elementary stream.

ATSC uses standard MPEG2 video. What is different about ATSC from Blu-Ray is the transport stream packaging. Do you need to make a transport stream? If so, what format?

[duffbeer911]

it is playing on an alcorn hardware player.. the specs for the encode are:

Encoded files must comply to ISO/IEC Specification 13818-2
MPEG2 files must be encoded as a Transport Stream.
Elementary Video stream must be Main Profile High Level MP@HL 4:2:0.
Elementary Audio Stream is required and must be AC3 or MPEG1 layer II encoded. Bitrates of 192, 224, or 384 kbps are supported.
Source audio before encoding is 16 bit at 48 or 44.1 kHz sample rate.
Transport stream packet size is 188 bytes or 224 bytes.
Stream must start with an I frame and finish on a 188 bytes packet boundary.
The two main resolutions supported are 1920 x 1080 x 29.97 (or 30) interlace and 1280 x 720 x 59.94 (or 60) progressive.
Recommended Video PID numbers are 0x11, 0x21 & 0x31. Audio PID numbers are video PID +3. Try to ensure that all files are encoded with the same PID. We Typically use 0x31 which is 49 in decimal.
ATSC bit rate is 19.39Mb/s. Higher bit rates up to 50Mb/s can be accommodated.
Constant Bitrate (CBR) or Variable Bitrate (VBR)
Group of Picture (GOP) Structure is CLOSED.
Normally 13 or 15 frames / GOP.
I B & P frames will provide the most efficient compression.
Preferably each GOP will contain a sequence header.

Using mainConcept i can do a blu-ray encode that does play but the motion isn't smooth... and then if i try to do an ATSC it won't let me do 25fps... i have not tried HCEnc yet - do you think it could meet those specs?

Thanks so much for your help

[Guest]

Answers regarding HCEnc:

Encoded files must comply to ISO/IEC Specification 13818-2 OK.

MPEG2 files must be encoded as a Transport Stream. HCEnc make video elementary streams, i.e., m2v. You would need to use a multiplexer after encoding. One possibility is XMuxer Pro. A more expensive but more capable one is Manzanita Muxer.

Elementary Video stream must be Main Profile High Level MP@HL 4:2:0. OK.

Elementary Audio Stream is required and must be AC3 or MPEG1 layer II encoded. Bitrates of 192, 224, or 384 kbps are supported. You can make your audio stream with one of several available high-quality freeware tools. Then you mux it in with the video.

Source audio before encoding is 16 bit at 48 or 44.1 kHz sample rate. See above.

Transport stream packet size is 188 bytes or 224 bytes. 224 is unusual (did you make a typo; 204 is usual) but both muxers I mentioned do standard 188 byte packets. Manzanita might do 224 as well.

Stream must start with an I frame HCEnc will do that.

and finish on a 188 bytes packet boundary. The muxer will do that.

The two main resolutions supported are 1920 x 1080 x 29.97 (or 30) interlace and 1280 x 720 x 59.94 (or 60) progressive. OK.

Recommended Video PID numbers are 0x11, 0x21 & 0x31. Audio PID numbers are video PID +3. Try to ensure that all files are encoded with the same PID. We Typically use 0x31 which is 49 in decimal. Both muxers allow you to set the PIDs as required.

ATSC bit rate is 19.39Mb/s. Higher bit rates up to 50Mb/s can be accommodated. Both muxers allow you to create CBR transport streams with specified bitrate.

Constant Bitrate (CBR) or Variable Bitrate (VBR) Both muxers support both of these.

Group of Picture (GOP) Structure is CLOSED. You can tell HCEnc to close GOPs.

Normally 13 or 15 frames / GOP. You can define the GOP structrure in HCEnc.

I B & P frames will provide the most efficient compression. See above.

Preferably each GOP will contain a sequence header. I belive HCEnc will do that.

[duffbeer911]

thanks for all that detail .. it sounds like HCenc is a great little application .... one question though, what would be the best way to get a 1920x1080 uncompressed (.mov) source into HCenc?
I'm searching around the net for some info, but everything I find is about ripping DVDs or converting mpegs ... where as I just need to work with my original source...

thanks!

[Guest]

what would be the best way to get a 1920x1080 uncompressed (.mov) source into HCenc? Please read and follow our forum rules, specifically, rule 12: do not ask what's best.

What are these mov files and where did you get them?

[duffbeer911]

ooops... sorry about the rules :-) .... I should re-word it to "How do you get uncompressed 1920x1080i 25fps .mov into HCenc?"

-we have made the source ... it comes out of finalcut and after effects. The files are 1920x1080i @ 25fps uncompressed quicktime movies. We can convert them to whatever file type, i just don't want to compress the files twice.
It looks like HCenc can do the mpeg2 encodes that we need (whereas the purchased encoder can't!) ... any help would be fantastic

thanks very much

[Guest]

DirectShowSource() ?

[duffbeer911]

sorry for the simple questions ... where do I run DirectShowSource() ? i haven't done anything script based like this so it's all a little confusing ...

[Guest]

It's an Avisynth source filter.

www.avisynth.org

http://avisynth.org/mediawiki/DirectShowSource

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2005-08,GGLD:en&q=opening+mov+files+in+Avisynth

[duffbeer911]

thanks ... so i've installed avisynth and HCenc is detecting it OK ... then I made a .avs script file that just has the
DirectShowSource("path to file")
command in it. Is that all I need in the .avs file to import it into HCenc?

... once I get the file into HCenc I should be ok with the rest of it :-)

cheers

[Guest]

Did you try it?

You can try opening the AVS script in VirtualDub and see if you see frames.

[duffbeer911]

i tried it in both virtualdub and HCenc but they both just freeze up ...

DirectShowSource("path to file")
is the only line I have in the .avs file - does that sound right?

[duffbeer911]

ok, so i left it while it was frozen and it finally came up with an error saying "file type not supported" ... this is a quicktime movie with compression set to none ... maybe i should try it as an AVI set to NONE

[duffbeer911]

hi again ... sorry to keep smothering you with questions ... but just quickly back to your original comment about blu ray being packaged differently than ATSC because of the transport stream ... if I was to make a generic mpeg2 that fit all the other specifications as an elementary stream and then multiplex them into a transport stream is that the same as an ATSC mpeg2? or are there other differences?

thanks again!

[Guest]

The Wiki I linked describes other options for opening MOVs. You should also open another thread about it in the approriate forum. Guys that can help you will not see your issue here as it is off topic for this thread title and forum.

Regarding the transport stream. We have already covered point-by-point your stated requirements and decided that they could be met. What doubts are you having now?

[duffbeer911]

sorry i re-read your first response and it makes sense ...

i've have been able to successfully make a transport stream that plays and spatially looks great ... there is just a problem with the motion ... it stutters for a millisecond about once every second, then plays fine for a second, then stutters etc etc etc ... it continues to do this consistently through the video. It is definitely not interlace jitter. Maybe something to do with the GOP? maybe it is stuttering at the start of every GOP? or maybe the player is trying to do an NTSC convert? I don't know ... i might make a new post, because as you said, this thread is getting off topic..

thanks so much for your detailed help with this