How much 1080i will fit on a 25gb Bluray?
 

How much 1080i footage will normally fit on a 25gb disc when using the Mpeg 2 for bluray template? I don't know how long my current project will be for sure, but it looks to be around 02:45 in length so far. I'm hoping to not have to need a 50GB disc, they are SO expensive.

Re: How much 1080i will fit on a 25gb Bluray?
 

Here is how to calculate the bitrate:

Step 1: A 25GB disk has 25*1000*1000*1000*8 = 200000000000 bits
Step 2: 2:45 hours is (2*60+45)*60 = 9900 seconds
Step 3: Divide to get 200000000000/9900 = 20202020 bps = 20 mbps

Conclusion: After taking audio, menus and other overhead into account an 18 mbps encode should easily fit. Many people consider 18 mbps enough for H264 but too low for mpeg2. My advice is to use H264 encoding.

Re: How much 1080i will fit on a 25gb Bluray?
 

Thank you for your calculations, Eric!

Re: How much 1080i will fit on a 25gb Bluray?
 

I tried Sony AVC for bluray for the first time, it is amazing. The quality seems very high, and it takes half the room of Mpeg 2. It takes SO long to render though.

Re: How much 1080i will fit on a 25gb Bluray?
 

Yes, it takes so long to render, but that's what night times are for. My question concerns replay - is MPEG2 BD easier for a Blu-ray player to decode and display rather than the more compressed more modern and less space-consuming MPEG4?

tom.

Re: How much 1080i will fit on a 25gb Bluray?
 

Please, someone answer Tom's question. My project is a wedding video. Will it play in most Bluray players if I render to mpeg 4?

I would like to know this before I send out 5 discs to a customer! I had never even thought of the ramifications of playback before I rendered.

Re: How much 1080i will fit on a 25gb Bluray?
 

Technically, it shouldn't make any difference in playback as long as the video is rendered to a blu-ray specified format and is within the *maximum* bit-rate for that format.

In reality, the player will use more computing energy to decode AVC since it is a more complex format than MPEG-2 - but the player is supposed to be designed to handle this.

All said, it is PC-based software players where you may experience problems. This is because the player may contend for resources with other applications that are also running. MPEG-2 may 'play' better on a 'busy' computer since it will not require as much computing time. In contrast, a hardware-based blu-ray play such as one you would hook to your TV set would have no problems - it's processor runs in a closed environment.

Re: How much 1080i will fit on a 25gb Bluray?
 

Thanks for your post Gene, very reassuring. I have noticed issues playing factory pressed Blurays on my PC, which is frustrating when I have a fairly powerful machine. They do play, but on occasion I will have to restart the application as it won't always work first time.

Thanks again, very much, for your response.

Re: How much 1080i will fit on a 25gb Bluray?
 

@ Gene and Eric, I'm confused on mpeg 2 for bluray. Can I lower the bit rate to say 20mbps and will it still work for Bluray? How badly will the images suffer I wonder? Would the file still work fine with Bluray discs in DVDA?

The Sony AVC codec is taking MUCH too long, I have too much work to do to wait for these insane render times, but my project when rendered to 25mbps mpeg 2 is too large.

Your thoughts?

Re: How much 1080i will fit on a 25gb Bluray?
 

Jeff. this may be of interest.
AVC for Blu-ray Encoding | NetBlender

Re: How much 1080i will fit on a 25gb Bluray?
 

Thanks Colin, interesting. As a Vega user I don't see where it fits in for me but it's good to know about.

Re: How much 1080i will fit on a 25gb Bluray?
 

For mpeg2 at 20mbps or 18mbps I would downscale to 1440x1080i while rendering. This gives the encoder less data to compress and can result in higher quality at low bitrates.

Re: How much 1080i will fit on a 25gb Bluray?
 

Thanks Eric. I'm currently encoding at 1080 18mbps to see how it plays, it's taking 2.5 hours as opposed to almost 5 with Sony AVC.

Re: How much 1080i will fit on a 25gb Bluray?
 

It will be interesting to hear how much quality difference you notice between the two codecs.

Re: How much 1080i will fit on a 25gb Bluray?
 

They look identical to me.