Blu Ray LPCM or PCM? That is the question...

[hinsdale1]

I am converting my hd and sd music videos and want to keep them in a container that will allow for seamless conversion to Blu Ray burns (no transcoding) as needed.

I am using h.264 for the video and audio sources are LPCM. When i use mkvmerge to mux the audio and video, the mkvmerge program seems to automatically demux the LPCM wav audio file and then covert to PCM module. The resulting .mkv has PCM audo instead of the original LPCM (not really sure of the difference).

The resulting mkv files play fine on my computer players with the lossless audio. However, when i burn (using MultiAVCHD) the resulting mkv files to Blu Ray format (m2ts), and load the iso into PowerDVD there is no sound. I understood that Blue Ray supports LPCM .. does it not support PCM? And is there another container (m2ts, ts, etc) that will preserve the LPCM? Does .mkv not support LPCM (why does mkvmerge convert the audio)?

Any help or suggestions would be greatly appreciated!!!

[mrswla]

Linear Pulse Code Modulation (LPCM) and Pulse Code Modulation (PCM) are basically the same thing. I wouldn't put too much faith in PowerDVD. I could never get it to play any blu rays. Try burning to a BD-RE and play on a ps3 or stand alone player.

Oh, and welcome to the forum

[hinsdale1]

Thank you for your answer and my welcome nice to join.

Unfortunately, I dont have a standalone blue ray player yet - just the PowerDVD. (Just thinking ahead in terms of compatabiliy).


Are you fairly certain of the compatiblity of the PCM (Blu Ray specs specifically say LPCM)?

They are both 16bit 48000hz 2 channel but there must be some important difference otherwise why would the mkvmerge program go thru the trouble of converting the LPCM to PCM first, why not simply mux the h.264 with the existing LPCM? Does anyone know if .mkv doesnt support LPCM only PCM?

When I burn these pcm .mkv files with MultiAVCHD, the resulting .m2ts file shows (with mediainfo) audio there (listed as pcm) but not only will PowerDVD not play them but none of the players I have will play the m2ts files with sound. When I drop the file in Graphedit, the sourse splitter (Hailli) doesnt even recognize an audio output - just a pin for the video output to the decoder. I reaize this could be a codec issue, but there is no problem when using the LPCM audio.

However, If I load the resulting .h264 + pcm .mkv file into MultiAVCHD and then replace the pcm audio with the original LPCM audio, then the resulting blu ray plays fine in PowerDVD.


Anywy, just want to be sure that these new pcm .mkvs i am going to make will work for blu ray... or if someone can suggest another conatiner that keeps the original LPCM.. thanks for any help

[aedipuss]

strictly speaking lpcm is the standard used by dvd and blu-ray. pcm in general is the same and the term is sometimes used interchangeably with lpcm, but there are other types of pcm that are not usable in video.

[Cornucopia]

For any purposes you would be using, PCM and LPCM are the SAME thing.

(HUNCH):
The problem might lie in the file's BYTE ORDER (Intel's LSB vs. Motorola's MSB). To be a valid DVD or Blu-Ray audio, PCM (or LPCM if you will) must follow the spec to the letter. IIRC, it's Motorola MSB (that's Most-Significant-Bit) ordering to you.

Mkvmerge must want to flip the byte ordering for some reason. Not familiar enough with the app to know if there's a switch for avoiding this (the choice whether to flip or not is common enough in DVD encoding/muxing apps). Check your apps (both encoding, muxing and playing), some will support one, some the other, some both.

Scott

[poisondeathray]

If you want to keep it as LPCM, just use a transport stream instead (e.g. tsmuxer, multiavchd). Retail blu-ray's come as LPCM , not PCM, but if you wanted to switch, you could use eac3to to convert. As mentioned above , all that is changed is a byte header.

If you are authoring for blu-ray this makes sense anyway. Not sure why you would go to .mkv then to .m2ts, as it's an uncessary step. If you encode your assets, you leave them unwrapped until you are ready to author (raw avc, raw lpcm).

[hinsdale1]

thanks scott,

Maybe there is an mkv expert who can tell me why the conversion

As I said I can play the resulting PCM .mkv's fine on my pc... love the mkv format... just want to be sure that they will play in Blu Ray players as m2ts without converting the audio back to LPCM when comes time to burn. I looked hard for some method to disable the conversion or an explanation as to why it converts but can find nothing.
Is there another MkV muxer that might do it differently? Seems like mkvmerge is the recommended choice ... maybe some very kind sole will burn an .mkv (with LPCM source) created by mkvmerge and see if the resulting blu ray works

[hinsdale1]

If you want to keep it as LPCM, just use a transport stream instead (e.g. tsmuxer, multiavchd). Retail blu-ray's come as LPCM , not PCM, but if you wanted to switch, you could use eac3to to convert. As mentioned above , all that is changed is a byte header.

If you are authoring for blu-ray this makes sense anyway. Not sure why you would go to .mkv then to .m2ts, as it's an uncessary step. If you encode your assets, you leave them unwrapped until you are ready to author (raw avc, raw lpcm).

Actually this is very helpful.. I guess I was trying the .mkv route because I knew Windows 7 Media Center (dont use much currently but may use in future) will play .mkv's (which can preserve my lossless audio) and .mp4s (dont believe these handle lossless audio) and .mkv seems to be the favorite format. Are there any downsides to using .m2ts or .ts containers? Size, compatiblity with players, windows media center compatibility. Anybody think of a reason this isnt the perfect solution?

[poisondeathray]

The 1 downside is overhead size is about 6-7% larger than .mp4 or .mkv . But if you are using a blu-ray player (not a blu-ray player with mkv support and not a htpc or mediabox like wdtv), then you have to use .m2ts anyway. Overall, a transport stream will be compatible with more devices than .mkv

Most PC software "prefer" PCM as opposed to LPCM. This includes video editors, audio editors, audio utilities etc...Perhaps this is why mosu (the mkvmerge author) programmed it that way?

But .mkv has much more utilty and supports many more formats, attachements, subs, fonts etc.. But this doesn't matter if you intended target is a conventional blu-ray player

[hinsdale1]

The 1 downside is overhead size is about 6-7% larger than .mp4 or .mkv . But if you are using a blu-ray player (not a blu-ray player with mkv support and not a htpc or mediabox like wdtv), then you have to use .m2ts anyway. Overall, a transport stream will be compatible with more devices than .mkv

Most PC software "prefer" PCM as opposed to LPCM. This includes video editors, audio editors, audio utilities etc...Perhaps this is why mosu (the mkvmerge author) programmed it that way?

Thanks again for everyones help... this is a great forum.

I realize that i have to use .m2ts for blu ray discs... but there was no transcoding needed for .mkv files (with compliant sizes, framerates and lpcm audio) to .m2ts anyway, so seemed the logical choice.. And i have a lot of non-compliant mis-sized videos that I would rather not transcode presently in order to store as .mt2s ... and for these I would rather for the time being (without re-encoding) transfer now to .mkv with LPCM audio (I replace the compressed aac,ac3,mp3 audio with lossless sourse during the conversion - just takes a few minutes once u get some practice) that will play perfectly on the PC now (even if they are non-compliant for blu ray) and can transcode to .m2ts if/when the time comes later.

What I worry about is later when comes time to burn these pcm .mkv files to Blue Ray - will i then not only need to transcode the video of these non-compliant .mkv files but will I also need to convert the audio from the pcm (that mkvMerge created) back to LPCM in order to use for Blu Ray. I know this is an easy conversion but would rather not have to add any more steps when comes time for conversion (talking about thousands of high quality music videos).


Your answers have been very helpful in narrowing down the options. I can store my compliant videos in .m2ts. But I still have the LPCM vs. PCM problem for the non-compliant videos that I dont want to re-encode right away.


It would be very helpful to know for certain if:

(1) the .m2ts files created from an MKVmerge .mkv file with pcm audio (converted automatically by MKVMerge from the source LPCM) will play in a Blu Ray player.

(2) And if not, is anyone aware of an .mkv muxing tool that doesnt automatically convert LPCM to PCM.

[mrswla]

It would be very helpful to know for certain if:

(1) the .m2ts files created from an MKVmerge .mkv file with pcm audio (converted automatically by MKVMerge from the source LPCM) will play in a Blu Ray player.

How large is your .m2ts file? If you want to send it to me via e-mail, I will burn to a bd-re and see if it plays on a ps3.

[hinsdale1]

How large is your .m2ts file? If you want to send it to me via e-mail, I will burn to a bd-re and see if it plays on a ps3.

sorry for the delay in responding.. had puter crash... had to rebuild from scratch... thank you for the generous offer... file size is about 90MB.. to big for email i would think but can try and upload to rapidshare and give you a link if offer is still good... i have some other PAL compatility questions so might have a couple other samples to test.. so will post them all and can test them at same time.. will be tomorrow likely. Thanks again. Still very interested in the PCM vs LPCM issue.. think it may just be a codec issue on my PC hopefully and the PCM will hopefully work fine on Blu Ray players.

[Cornucopia]

The thing you still seem to be missing is that LPCM=PCM, unless you want to go the ADPCM realm (and no one really uses those anymore), or want to quibble with Byte Order.

Ok, let's say you started out with Motorola byte order (MSB). And your signal is this:

00101010
11111000
01001011
...

If they're converting for MKV into Intel byte order (LSB), it'll look like this:

01010100
00011111
11010010
...

See: they're the EXACT SAME DATA, but just spat out in reverse order! It's not like you're "losing quality" or changing the sound to something different.

Another conversion step (needed as you said for converting to Blu-Ray compatible) would just reverse the order again, resulting in the original order. No Loss. No harm, no foul. Stop worrying about it.

Scott

[hinsdale1]

Another conversion step (needed as you said for converting to Blu-Ray compatible) would just reverse the order again, resulting in the original order. No Loss. No harm, no foul. Stop worrying about it.

Scott

Thanks for the reply. Actually I did understand that there was no transcoding going on.... was never worried about any loss of quality. I understood that the pcm and lpcm were almost identical and that the container was just being slightly modified. Just wanted to know why mkvmerge was doing it (seems like adding a step for no reason .. unless there is a reason?)

and also that when comes time to convert the resulting mkv's to mt2ts blu ray format.. would i need to change it back to the recognized LPCM.. which means an extra step and although extremely simple conversion i am sure.. when considering hundreds (and even thousands of music videos if I get all my conversions done) is just something i wanted to avoid if possible... so still just looking to verify the PCM that mkvMerge creates will work without conversion back to lpcm (as simple/small as it may be).

[erek]

Is this Blu-Ray Disc Compliant? Also would going from Lossless x264 / PCM to DVD through HcEnc give better results than x264 / AAC @ 18Mbps?



GeneralUnique ID : 184693749673122937833259551724284816218 (0x8AF2B8E8E49162F9148A4A066CDA2B5A)Complete name : untitled.mkvFormat : MatroskaFormat version : Version 2File size : 86.9 MiBWriting application : Lavf53.21.1Writing library : Lavf53.21.1VideoID : 1Format : AVCFormat/Info : Advanced Video CodecFormat profile : High 4:4:4 Predictive@L5.1Format settings, CABAC : YesFormat settings, ReFrames : 16 framesCodec ID : V_MPEG4/ISO/AVCWidth : 1 920 pixelsHeight : 1 080 pixelsDisplay aspect ratio : 16:9Frame rate mode : ConstantFrame rate : 23.976 fpsColor space : YUVChroma subsampling : 4:2:0Bit depth : 8 bitsScan type : ProgressiveWriting library : x264 core 123 r2189 35cf912Encoding settings : cabac=1 / ref=16 / deblock=1:0:0 / analyse=0x3:0x133 / me=esa / subme=8 / psy=0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=0 / threads=4 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc=cqp / mbtree=0 / qp=0Default : YesForced : NoAudioID : 2Format : PCMCodec ID : A_PCM/INT/LITBit rate mode : ConstantChannel(s) : 2 channelsSampling rate : 48.0 KHzBit depth : 16 bitsDefault : YesForced : No

[poisondeathray]

Is this Blu-Ray Disc Compliant? Also would going from Lossless x264 / PCM to DVD through HcEnc give better results than x264 / AAC @ 18Mbps?



GeneralUnique ID : 184693749673122937833259551724284816218 (0x8AF2B8E8E49162F9148A4A066CDA2B5A)Complete name : untitled.mkvFormat : MatroskaFormat version : Version 2File size : 86.9 MiBWriting application : Lavf53.21.1Writing library : Lavf53.21.1VideoID : 1Format : AVCFormat/Info : Advanced Video CodecFormat profile : High 4:4:4 Predictive@L5.1Format settings, CABAC : YesFormat settings, ReFrames : 16 framesCodec ID : V_MPEG4/ISO/AVCWidth : 1 920 pixelsHeight : 1 080 pixelsDisplay aspect ratio : 16:9Frame rate mode : ConstantFrame rate : 23.976 fpsColor space : YUVChroma subsampling : 4:2:0Bit depth : 8 bitsScan type : ProgressiveWriting library : x264 core 123 r2189 35cf912Encoding settings : cabac=1 / ref=16 / deblock=1:0:0 / analyse=0x3:0x133 / me=esa / subme=8 / psy=0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=0 / threads=4 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc=cqp / mbtree=0 / qp=0Default : YesForced : NoAudioID : 2Format : PCMCodec ID : A_PCM/INT/LITBit rate mode : ConstantChannel(s) : 2 channelsSampling rate : 48.0 KHzBit depth : 16 bitsDefault : YesForced : No

No - Wrong level and profile, 16 reference frames, long keyframe interval to name a few of the problems

No - There is no way MPEG2 with any encoder will look better than properly encoded h.264 at equivalent bitrates at that range

AAC audio isn't blu-ray compliant



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