H.264 Bluray m2s bitrate question

[schmickers]

Hi all,

I have a JVC HD camcorder that saves to HDD. The files it produces are mpeg ts files, that I convert to mpeg files to be able to import into Adobe Premiere CS4.

I am trying to title these files and save them; I am aiming to save them as h.264 m2ts files so that they can be viewed on my home media player, but will also author to bluray disc with minimal fuss or recoding / transcoding. However, when I select the preset for h.264 m2ts bluray files in Adobe Media Encoder, the files it produces are far, far larger than the source files.

A look at the source files indicates they are 1920x1080 8000kbps mpeg files. However, the presets for h.264 bluray m2ts files seem to call for 1920x1080 output with a target bitrate of 25mbps. If the source files are essentially 8mpbs, is there any point in producing 25mbps outputs? Or can I expect to produce an 8mpbs h.264 encoded file with minimal loss of quality? If so, does that mean I can also fit a lot more video on a bluray disc?

[poisondeathray]

If the source files are essentially 8mpbs, is there any point in producing 25mbps outputs?

Probably not, but there will be less quality loss . 8Mb/s is very low for 1920x1080

Or can I expect to produce an 8mpbs h.264 encoded file with minimal loss of quality?

Probably , but it will depend how picky you are. Casual observer may not notice the difference , but there will be some degree of loss

If so, does that mean I can also fit a lot more video on a bluray disc?

Yes. Filesize = bitrate x running time



Are you sure the source files are 8Mb/s ? That's quite low for 1920x1080 and MPEG2 . That's a more reasonable bitrate for standard definition. How are you determining this ? You might benefit from denoising or deblocking. Try bitrate viewer and mediainfo to confirm what is going on

[schmickers]

Thanks for the speedy reply.

I have checked the file with MediaInfo - oddly, it reports its duration as 34 seconds, when in actual fact the file is 2 minutes and 14 seconds to watch. Obviously, MediaInfo also reports a higher bitrate, because it seems to think the
file is much shorter.

Bitrate viewer reports the duration correctly; 2:14, with the correct number of frames for that duration (25fps x 2:14 = 3350frames). It determines an average bitrate of 25000 kbps. And that adds up; 134 seconds x 25mbps equals 3350 megabits, which is just over 400 megabytes. So why when I encode the file as a bluray h264 compliant file does it come out as double that?

[schmickers]

Okay; just noticed that when I choose "TS" as the multiplexer in Adobe Media Encoder, the projected file size doubles; if I select "none" it remains comparable to the original, using a target bitrate of 25mbps. It also changes the file type, outputting as m4v instead of m2ts. Any video gurus out there able to explain why this is? I'm going to try encoding without multiplexing now and see what kind of result I get.

[poisondeathray]

What kind of audio and how many streams?

Transport stream container adds about 6-7% overhead over the elementary video. It needs to be wrapped in a transport stream eventually (you can let your authoring application do it)

IIRC the multiplexer is broken in AME anyway, and you usually don't want to multiplex if you're authoring for blu-ray (let the authoring tool like encore do it)

Run the encoded file through bitrate viewer as well - just because you entered 25Mb/s doesn't mean you achieved it.

[schmickers]

Dolby stereo. One audio, one video stream.

So, just say I select the standard profile for 1080i 25fps h.264 encoded video with dolby stereo audio, and it outputs in an m4v file. Will this later be problematic for bluray disc authoring?

[poisondeathray]

If you use the h.264 blu-ray preset it will be compatible. It will say "don't transcode" in encore (so it won't be re-encoded)

If you're using encore , you could use dynamic link as well, and let encore do the calculations to fit to disc (instead of guessing or using a bitrate calculator)

[edDV]

What JVC camcorder recorded these files? The format seems very strange.

If MPeg2, VC-1 or h,264, the original files should be usable in a Blu-Ray AVCHD file structure. No need to convert MPeg2 to h.264 especially if it is already 8 Mb/s.

You would need to change to m2ts transport stream.

[schmickers]

What JVC camcorder recorded these files? The format seems very strange.

I can't think of the model number ofh the top of my head, but the files it produces are TOD files, which I am unable to import into Adobe Premiere Pro. My workflow consists of pulling the files off the camcorder, running them through MPEGStreamclip, which converts them into standard mpeg files, which I can then import into Adobe Premiere Pro.

I'm only just learning about h.264 and the Bluray format, as this is the first HD camcorder I have had, so excuse my ignorance. I basically want to know what format to output my titled files to from Adobe Premiere Pro that will be maximally compatible with viewing on a computer or a media player (in my case, a WDTV Live) and ALSO able to be imported into a Bluray project in the future with a minimum of fuss and no need to transcode again.

If MPeg2, VC-1 or h,264, the original files should be usable in a Blu-Ray AVCHD file structure. No need to convert MPeg2 to h.264 especially if it is already 8 Mb/s.

Obviously, I'd prefer to avoid any conversion at all, but as I said above, Adobe Premiere Pro doesn't support TOD files, so I need to convert them just to import them. MPEGStreamclip seems to go through them very quickly, though, so I don't think it is transcoding them or changing their content at all; I have always assumed it is just doing something to the file container to make them standard mpegs.

You would need to change to m2ts transport stream.[/QUOTE]

[edDV]

TOD files are standard definition 720x480i not 1920x1080i. 8Mb/s sounds about right for TOD.

TOD files are MPeg2 transport streams, not h.264.

Search this site or Google for TOD import Adobe Premiere Pro. With CS4 it may be as easy as changing the extension to mts or ts.

Your Premiere project should be set to DV (either 4:3 or wide).

[racer-x]

When using MperStreamclip to convert files without re-encoding, it uses an arbitrary 8 mbps bitrate flag. That is incorrect and the true bitrate of the 1080i files are likely to be 25 ~ 28 mbps. When you import your TOD files into MpegSteamclip, choose Save As and save at "TS". Premiere should handle those just fine

[schmickers]

Thanks so much for your help, guys.

They are definitely HD video - I wonder if you are thinking of MOD files? Thank you for the advice RE MPEGStreamclip, I will try converting them to TS files.

So, my final question: what format should I encode to from titling in Adobe Premiere Pro? Of course, I am aware that an encoding will be lossy, so that is why I want to try and find an output format that minimises lossiness, and will not require re-encoding when I eventually author to Bluray.

[edDV]

It would sure help if we knew the JVC camcorder model and the mediainfo data for the files.

[schmickers]

It is a GZ-HD6AA.

[edDV]

Read all of this page. The GZ-HD6AA records to MPeg2 transport streams.
http://www.camcorderinfo.com/content/JVC-Everio-GZ-HD6-Camcorder-Review-34759/Format.htm

Your 8 Mb/s bit rate doesn't show up on the list. Somehow you converted these files and over-compressed them.

Supported recording modes are
1440 CBR records at 1440 x 1080 at a fixed 27 Mbps MPeg2
and is directly compatible with HDV format for editing.
FHD, records 1920 x 1080 at an average 26.6 Mbps VBR MPeg2.
SP, records 1920 x 1080 at an average 19 Mbps VBR MPeg2.
LP records 1920 x 1080 at an average 11.1 Mbps MBR MPeg2.

After re-wrapping from TOD (M2t) to m2ts, all of these formats are likely to play in a Blu-Ray ADVHD file structure without lossy codec conversion.

Use MultiAVCHD to author the disc.