How Much Anime Can REALLY Fit On A Blu-ray?

by Justin Sevakis,

Mike (Toole) asks:

How much anime will fit on a single Blu-Ray disc? Is a single BD-50 really enough for 13 episodes of subtitled 1080p anime?

How much anime can comfortably fit onto a dual layer Blu-ray in full HD? For those who don't know, a dual layer Blu-ray can fit around 50 GB of data -- although, after formatting and other overhead, it's closer to 44 GB. When a disc author (such as myself) creates a disc, they have to do some math to figure out their encoding settings in order to fit everything onto the disc, while giving as much data space to the program video as possible. Generally, the more breathing room you can give the program, the "better" the video quality. Theoretically, anyway.

However, Blu-rays are expensive to mass produce (still 4-5x the price of a DVD at low print runs), so a few publishers have taken to cramming entire seasons of full HD anime -- up to 13 episodes and some extras -- on a single disc, subtitled-only. The thinking is that these discs won't sell very many units (hence, their being released subtitled-only in the first place), so the publisher is trying to keep authoring and replication costs down as well. But some fans have expressed concern that this might be squeezing the video too much, and that quality will suffer.

I was recently asked to produce several discs like this (I will not name them here for myriad political reasons), and I did so very, very carefully. Putting 9 episodes on a disc (which is pretty common) means a video bitrate of around 25-30 Mbps, but 13 episodes can mean cutting that down to as low as 15 Mbps. I did a lot of tests before I agreed to do it. I was all ready to take some ragged looking screen shots and send them to the client with a note that said, "this really doesn't look good enough... Can we please go two discs on this?"

I... never got to send that note. My first tests, which were of an episode with a lot of CG explosions and action shots, looked absolutely fine. Further testing with newer digipaint shows didn't reveal any major problems either. There were a (very) few cases where a scene might have benefitted very very slightly from the additional space, but to be honest, it would've been very hard to tell the difference for me, let alone the average fan. I had to admit that I was absolutely able to release a good-looking disc with that much video on it. I still don't like doing it, but that's just because I sweat a lot more making discs like that.

There are some major exceptions to this. Any anime with film grain -- even sometimes the artificial film grain they put on newer digital shows -- can really run into problems at lower bitrates. Film grain is unpredictable random noise added to the picture, so compression technology is pretty bad at preserving it while throwing away enough data to fit the video into a small space. There was a very grainy movie from the 80s I made a disc for last year that had to be on a dual-layer disc because even at 25 Mbps we were running into quality issues. Additionally, having multiple audio tracks, or 5.1 surround audio, eats up a ton of space too.

There are exceptions in the opposite direction, too. Early digipaint shows, ones that were made in a relatively low resolution and/or printed to video with outdated video gear that introduced banding and other problems -- those shows I can squeeze down like crazy and not lose anything. All the already-existant video issues completely hide any new problems that might be occurring, and I can honestly not tell the difference between the masters and my final encodes.

There are some people that complain a lot about video bitrates, but most of them are complaining about numbers reported by disc disassembly and video analysis tools, not what they can actually perceive with their eyes. Once my work is done, if I were to spread the exact same encodes out onto two discs, nobody would notice anything amiss. Anime is easy video to compress for modern software, being mostly large swathes of solid color that don't move very much. A good encoder can really take advantage of the nature of those visuals and squeeze down the video file to an insane degree and really lose next to no quality, compared to live action material. However, not all encoding software is created equal, and some techniques will work way, way better than others. I can only vouch for my own work, not any general practice across the board. But the 13-episode discs I've seen from Sentai Filmworks, which I did not do, have looked fine.

But anime fandom always has that tiny handful of fans that SWEAR they can tell the difference, that our work looks like garbage, and that they're very, very angry. To which I can only shrug. Partly because I have to be able to trust my own eyes and judgement. By the time anyone sees the final product I've been done with it for months and 99.9% of customers -- many of whom are very discerning -- are just fine with it unless some really stupid mistake got through somehow. But mostly I shrug because everyone in every facet of this business gets those notes and some people are just unreasonably angry about everything.

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    Justin Sevakis has worked in the anime business for over 20 years. He's the original founder of Anime News Network, and owner of the video production company MediaOCD. You can follow him on Twitter at @worldofcrap.

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