Transcoding to AVC MKV Using BD Compliant Settings

[Agent 5]

I have recorded many TV shows via DVB in MPEG 2 video and MPEG 1 Layer 2 audio. The video bitrate was very high so I thought it would be best to transcode the video to AVC, leaving the audio as-is, and then authoring the result to BD Video. I used MeGUI to perform the transcoding, but it did not multiplex the audio because MP2 is not allowed in an M2TS container. I had no choice but to use the MKV container and decided that I would eventually just copy the MKV files to the BD, knowing that I would not be able to use it as a Video BD.

I used the same BD compliant settings for both containers, but because I will not be able to play the disc on a BD Player as a Video BD, is it necessary to keep the video BD Compliant? Will it be better to change some options to make the video compression more efficient? Here are my settings, which were taken from www.x264bluray.com:

x264 --bitrate XXXXX --preset veryslow --tune film --bluray-compat --vbv-maxrate 40000 --vbv-bufsize 30000 --level 4.1 --keyint 25 --open-gop --slices 4 --tff --colorprim "bt470bg" --transfer "bt470bg" --colormatrix "bt470bg" --sar 12:11 --pass 1 -o out.264 input.file

[jagabo]

I used the same BD compliant settings for both containers, but because I will not be able to play the disc on a BD Player as a Video BD, is it necessary to keep the video BD Compliant?

Don't count on BD players to be able to play anything beyond BD compliant settings. Regardless of container.

[poisondeathray]

You can use "2sec long GOP" settings, which double the GOP size and is still blu-ray compliant for SD bluray or HD bluray . Doubling the GOP length will significantly improve compression.

The drawback is you have to use <15Mb/s for maxrate, bufsize - but that usually is not an issue for SD video

For Level 4.0 you don't need 4 slices either (you don't need L4.1 for SD blu-ray) , this also improves efficiency by a tiny amount

You can read more about the rules here
http://forum.doom9.org/showthread.php?t=154533

[Agent 5]

Thanks for link.

I have a target filesize specified. If I change the keyint to 50, maxrate & bufsize to 15000, level to 4.0 (or should I go lower?) and slices to 1, will the resulting video have a better quality?

Will the MKV files that are created play on anything other than a PC, like a TV via USB or a BD Player that plays MKV files on BD? Are the changed settings still BD compliant? I think they are, if I understood the table in the link correctly.

[poisondeathray]

Thanks for link.

I have a target filesize specified. If I change the keyint to 50, maxrate & bufsize to 15000, level to 4.0 (or should I go lower?) and slices to 1, will the resulting video have a better quality?

This question is too vague. It depends on the source complexity, the bitrate you are using, relative to where you are on the compression curve

Raising the gop length will improve compression - so if you are bitrate starved, quality will be better (e.g. a noisy source, or lots of action) . If you are on the very high end of the compression curve (using lots of bitrate for very simple content, or very clean with little motion), it might actually be very slightly worse if you pixel peep

But most of the time, it will be better - "better compression" implies better quality at a given bitrate

Will the MKV files that are created play on anything other than a PC, like a TV via USB or a BD Player that plays MKV files on BD? Are the changed settings still BD compliant? I think they are, if I understood the table in the link correctly.

They are compliant, and should play on most devices.

But you should realize if you want it super strict for compliance, you should never put them into a container (leave as raw avc). As soon as you put into MKV (or any container), you irreversible change the sequence header and impair compatiblity in pro authoring tools) . Having said that - many players and consumer authoring programs won't mind - this is only if you are doing strict authoring

[Agent 5]

The content of the shows I want to transcode range from noisy to clean and from low motion to high action. I've done a few tests using the original settings, comparing the original to the transcoded, and to my untrained eye, I can't tell the difference. The video bitrate is about 1500kbps. Do you think with the bitrate and variety of content, the new settings will improve the quality?

Also, is it okay to use a level of 4.0, or would a lower level be better, or should I not specify a level so x264 will auto-detect it?

[poisondeathray]

The content of the shows I want to transcode range from noisy to clean and from low motion to high action. I've done a few tests using the original settings, comparing the original to the transcoded, and to my untrained eye, I can't tell the difference. The video bitrate is about 1500kbps. Do you think with the bitrate and variety of content, the new settings will improve the quality?

Also, is it okay to use a level of 4.0, or would a lower level be better, or should I not specify a level so x264 will auto-detect it?

Yes you will likely benefit in that bitrate range

For noisy sources, you will benefit far more from prepreprocessing and filtering

L4.0 is fine, or leave it auto . The point is not to use slices unless you have to (L4.1 for blu-ray requires it)

[Agent 5]

Should I leave slices out so it defaults to 0, or should I set it to 1?

[poisondeathray]

You can set it to zero or leave it out