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Bitstream Video on Blu-ray Players & Receivers

post #1 of 13
Thread Starter 
Hello everyone,

I'm new to the home theater world and recently found out that you can generally bitstream the audio from the Blu-Player device to your AVR so that it is the AVR who performs the actual decoding (provided it has support for that codec).

I'm just curious: Why isn't this feature (take the audio as it is on the disc and pass it along to the AVR) also available for the video stream? I googled for this but apparently this doesn't exist. I don't see any AVR announced with "h.264 decoding" nor I see a bitstream option for video on Blu-Ray devices (so that they can pass along the h.264 compressed video as it is).

I'm not complaining really. I'm just curious on why things are like this (for the audio side) but not the same for the video side. I'm wondering if there are technical limitations or just legal reasons (perhaps they don't want the h.264 encoded stream out of the Blu-ray player?) But then, it is allowed for audio so I don't get it.

Thanks in advance.

Regards,
Craconia
post #2 of 13
i'm confused by your post? What's wrong with the video the way it is sent from a blu ray player to the receiver?
post #3 of 13
Quote:
Originally Posted by Craconia View Post

Hello everyone,

I'm new to the home theater world and recently found out that you can generally bitstream the audio from the Blu-Player device to your AVR so that it is the AVR who performs the actual decoding (provided it has support for that codec).

I'm just curious: Why isn't this feature (take the audio as it is on the disc and pass it along to the AVR) also available for the video stream? I googled for this but apparently this doesn't exist. I don't see any AVR announced with "h.264 decoding" nor I see a bitstream option for video on Blu-Ray devices (so that they can pass along the h.264 compressed video as it is).

I'm not complaining really. I'm just curious on why things are like this (for the audio side) but not the same for the video side. I'm wondering if there are technical limitations or just legal reasons (perhaps they don't want the h.264 encoded stream out of the Blu-ray player?) But then, it is allowed for audio so I don't get it.

Thanks in advance.

Regards,
Craconia

Actually, this is a perfect question and one that has not been talked about much. Before HDMI became the standard, one of the avenues that CE manufacturers were going was Firewire (also known as IEEE 1394 or iLink). If you remember, even though it was invented by Apple originally in the 90s it was made an IEEE standard. With 400Mb/sec bandwidth for the IEEE 1394a standard, and isochronous transfer capability and daisy chaining, etc, and power carrying capability, it was ideal for home AV network. Several cable boxes had Firewire, the D-VHS VCRs did, my JVC TV from a few years ago did, all miniDV and DV cameras did and still do.

Firewire also supported an encryption protocol so that it would keep the studios satisfied. But, the studios were not satisfied. They demanded uncompressed video so that people that do break the HDMI encryption will be left with uncompressed HD video that would fill up hard drive in a jiffy and would be unmanageable for most people to copy. Recompressing uncompressed video is a long process. Uncompressed video will make one movie occupy more than a terabyte.

I even heard from unofficial sources that firewire could become a standard for Bluray but that never happened. Basically, if all TVs had firewire, then you could just connect them with firewire and the actual decoding of video would take place in the TV. Also, you could daisy chain all your AV devices with firewire and they will all auto discover each other and arbitrate and take care of bandwidth, isochronous (time dependent), etc. It would have worked wonders. It already did 10 years ago. But alas, we are left with HDMI and its revisions and problems.

Firewire has been relegated to a niche even by Apple. USB2 rules even though it is much inferior. USB3 is coming up. Thunderbolt aka Light Peek is still in its infancy.

I guess HDMI is here to stay since even DisplayPort (the true successor to DVI) has not taken off.
post #4 of 13
Quote:
Originally Posted by bommai View Post

Firewire also supported an encryption protocol so that it would keep the studios satisfied. But, the studios were not satisfied. They demanded uncompressed video so that people that do break the HDMI encryption will be left with uncompressed HD video that would fill up hard drive in a jiffy and would be unmanageable for most people to copy. Recompressing uncompressed video is a long process. Uncompressed video will make one movie occupy more than a terabyte.

I don't see how that answers the OP's query. According to your argument sending the compressed encrypted stream out to HDMI (what the OP is asking) is actually to the user's advantage as it takes up less space, not the other way round. It's possible studio want copy protection to be dealt with inside the player (player keeps the keys) and not elsewhere. In any case people have broken copy protection to rip to the HDD and for that matter HDMI encryption.

Another reason I see the way it's done is when you connect the player directly to TVs the TVs don't have video decoding abilities. It's always like this for DVDs and set-top boxes.
post #5 of 13
Quote:
Originally Posted by Kilian.ca View Post

I don't see how that answers the OP's query. According to your argument sending the compressed encrypted stream out to HDMI (what the OP is asking) is actually to the user's advantage as it takes up less space, not the other way round. It's possible studio want copy protection to be dealt with inside the player (player keeps the keys) and not elsewhere. In any case people have broken copy protection to rip to the HDD and for that matter HDMI encryption.

Another reason I see the way it's done is when you connect the player directly to TVs the TVs don't have video decoding abilities. It's always like this for DVDs and set-top boxes.

I will let the OP be the judge of that. I think he was just curious about why things are the way they are. I thought I did a pretty good job explaining the situation. Again, if you want bitstream audio out the Bluray player, the AVR has to support bitstream audio. If the bluray player is unable to also send a down converted 2.0 PCM, you will require an AVR with bitstream and a direct connection to TV is impossible. That is why ALL BD players have a PCM 2.0 down convert.

Is it that hard to imagine a TV that has a firewire port and can handle compressed video transmitted as DV stream. My JVC TV did precisely that. I could connect my camcorder directly to it using firewire and play my movies. Albeit, this was SD and not HD, but remember the bit rate required for HD is well within the capability of firewire 400Mbit/sec.

Again, there is nothing preventing someone to figure out a way to send compressed video through HDMI but the studios did not want that since they want the uncompressed video to be a natural barrier to capturing - again uncompressed video is about 1TB/movie approx.
post #6 of 13
As I understand what comes off the decoder into HDMI isn't 'uncompressed' video, in the sense of having 1920x1080x4x24=199,065,600 Bytes (or 1592,524,800 bits) per second. Your 1TB per movie argument to capture all that doesn't apply.
post #7 of 13
Thread Starter 
Kilian.ca,

I didn't mentioned encryption because that's a given (the decryption by the Blu-ray player). The default system is (roughly) for the Blu-Ray Player to decrypt the stream, decode (decompress the audio) and then transfer the PCM stream to the AVR. If you select the "Bitstream Option" on your Blu-ray then the audio decoding is skipped. In that context (where decryption already happened) is that I questioned the lack of a bitstream option for video.

Regarding your last post: What makes you think that what comes out of the Blu-ray player isn't uncompressed (for the video portion)? AFAIK the player is the one who decodes the h.264 stream since your TV or AVR doesn't have a h.264 decoder.

Bommai,

That's a good point: make it unpractical to capture the video since it is HUGE. I never thought about that. That makes perfect sense but, as Kilian.ca mentioned, the copy-protection have been broken enabling people to grab the unencrypted audio & video streams. Of course, that's with a general purpose computer like a PC. My original question was in the context of a home theater (a more closed system) and, again, I think you've nailed it. I don't see any other reason.

Thanks for your input Bommai & Kilian.ca.
post #8 of 13
While aacs and bd-java are broken, I don't think Netflix or iTunes encryption for bd movies have been broken. I think the studios were aware that they need two ways to prevent piracy. One with encryption and the other uncompressed video. So while bd movies can be directly ripped from the disc, capturing netflix, etc are harder.
post #9 of 13
What do you mean by Netflix encryptionnot being broken? I have been downloading and saving Netflix videos as AVI, or MS dvr files, or WTV files for about three years now. There are many programs that will save Itunes, Netflix, Amazon, Youtube etc as standard files on your computer.

one of them is playonit by media mall. cheap and easy and works as a plug in for WMC.
post #10 of 13
Quote:
Originally Posted by Craconia View Post

What makes you think that what comes out of the Blu-ray player isn't uncompressed (for the video portion)?

This was discussed in our HDTV Software Media forum where this thread really belongs. If you think what you get is uncompressed studio master with each pixel in each frame fully encoded with each primary colour (where the '1TB' comes from and which the whole argument entirely depends on) then you will be hugely disappointed.

Think about it: if you are getting uncompressed video then it shouldn't matter what codec is used and after decoding they would all be the same whether you use mpeg-2, VC-1 and AVC (h.264). But are they?
post #11 of 13
Quote:
Originally Posted by Kilian.ca View Post


This was discussed in our HDTV Software Media forum where this thread really belongs. If you think what you get is uncompressed studio master with each pixel in each frame fully encoded with each primary colour (where the '1TB' comes from and which the whole argument entirely depends on) then you will be hugely disappointed.

Think about it: if you are getting uncompressed video then it shouldn't matter what codec is used and after decoding they would all be the same whether you use mpeg-2, VC-1 and AVC (h.264). But are they?

You are confusing lossless versus uncompressed. I am not talking about lossless. What I am referring to is the fact the player decompresses the lossy encoded h.264 before placing it on hdmi to the display. This is similar to iTunes playing a mp3 file and sending it optically to a dac. If you watch the bitrate coming to the dac you have 16 x 44.1 kHz x 2 bits/sec, but the original audio file could be the lossy 128kbit/sec file. Same with video. We will probably never have lossless compression on video.
post #12 of 13
Video compression is lossy, that's generally understood. You don't understand PCM is constant bitrate but video can be V(variable)BR? What is video decompressed into that is the equivalent of PCM? You think lossy video takes up as much bitrate as original? You think a video with little motion takes up as much bitrate (therefore space) as one with lots of motion? You think a P or B frame take up as much bitrate as an I frame? Or a 4:2:0 scheme takes up as much bitrate as 4:4:4?
post #13 of 13
Curious questions. What format video does the tv see on its hdmi input when it is receiving say 1080p 24 bit 24 fps video. Is the tv aware of the P B and I frames? Is the tv aware of still pictures vs high motion pictures? Does the tv know about the compression schemes so that it can decompress?
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