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• Announcing the first free software Blu-ray encoder

  25 avril 2010, par Dark Shikari — blu-ray, x264

  For many years it has been possible to make your own DVDs with free software tools. Over the course of the past decade, DVD creation evolved from the exclusive domain of the media publishing companies to something basically anyone could do on their home computer.

  But Blu-ray has yet to get that treatment. Despite the “format war” between Blu-ray and HD DVD ending over two years ago, free software has lagged behind. “Professional” tools for Blu-ray video encoding can cost as much as $100,000 and are often utter garbage. Here are two actual screenshots from real Blu-rays : I wish I was making this up.

  But today, things change. Today we take the first step towards a free software Blu-ray creation toolkit.

  Thanks to tireless work by Kieran Kunyha, Alex Giladi, Lamont Alston, and the Doom9 crowd, x264 can now produce Blu-ray-compliant video. Extra special thanks to The Criterion Collection for sponsoring the final compliance test to confirm x264′s Blu-ray compliance.

  With x264′s powerful compression, as demonstrated by the incredibly popular BD-Rebuilder Blu-ray backup software, it’s quite possible to author Blu-ray disks on DVD9s (dual-layer DVDs) or even DVD5s (single-layer DVDs) with a reasonable level of quality. With a free software encoder and less need for an expensive Blu-ray burner, we are one step closer to putting HD optical media creation in the hands of the everyday user.

  To celebrate this achievement, we are making available for download a demo Blu-ray encoded with x264, containing entirely free content !

  On this Blu-ray are the Open Movie Project films Big Buck Bunny and Elephant’s Dream, available under a Creative Commons license. Additionally, Microsoft has graciously provided about 6 minutes of lossless HD video and audio (from part of a documentary project) under a very liberal license. This footage rounds out the Blu-ray by adding some difficult live-action content in addition to the relatively compressible CGI footage from the Open Movie Project. Finally, we used this sound sample, available under a Creative Commons license.

  You may notice that the Blu-ray image is only just over 2GB. This is intentional ; we have encoded all the content on the disk at appropriate bitrates to be playable from an ordinary 4.7GB DVD. This should make it far easier to burn a copy of the Blu-ray, since Blu-ray burners and writable media are still relatively rare. Most Blu-ray players will treat a DVD containing Blu-ray data as a normal Blu-ray disc. A few, such as the Playstation 3, will not, but you can still play it as a data disc.

  Finally, note that (in accordance with the Blu-ray spec) the disc image file uses the UDF 2.5 filesystem, which may be incompatible with some older virtual drive and DVD burning applications. You’ll also need to play it on an actual Blu-ray player if you want to get the menus and such working correctly. If you’re looking to play it on a PC, a free trial of Arcsoft TMT is available here.

  What are you waiting for ? Grab a copy today !

  UPDATE : Here is an AVCHD-compliant version of the above, which should work better when burned on a DVD-5 instead of a BD-R. (mirror)
  

  What’s left before we have a fully free software Blu-ray creation toolkit ? Audio is already dealt with ; AC3 audio (aka Dolby Digital), the format used in DVD, is still supported by Blu-ray, and there are many free software AC3 encoders. The primary missing application is a free software Blu-ray authoring tool, to combine the video and audio streams to create a Blu-ray file structure with the menus, chapters, and so forth that we have all come to expect. But the hardest part is dealt with : we can now create compatible video and audio streams.

  In the meantime, x264 can be used to create streams to be authored using Blu-Print, Scenarist, Encore or other commercial authoring tools.

  More detailed documentation on the new Blu-ray support and how to use it can be found in the official commit message. Do keep in mind that you have to export to raw H.264 (not MKV or MP4) or else the buffering information will be slightly incorrect. Finally, also note that the encoding settings given as an example are not a good choice for general-purpose encoding : they are intentionally crippled by Blu-ray restrictions, which will significantly reduce compression for ordinary non-Blu-ray encoding.

  In addition to Blu-ray support, the aforementioned commit comes with a lot of fun extras :

  x264 now has native variable-framerate ratecontrol, which makes sure your encodes get a correct target bitrate and proper limiting of maximum bitrate even if the duration of every frame is different and the “framerate” is completely unknown. This helps a lot when encoding from variable-framerate container formats such as FLV and WMV, along with variable-framerate content such as anime.

  x264 now supports pulldown (telecine) in much the same fashion as it is handled in MPEG-2. The calling application can pass in flags representing how to display a frame, allowing easy transcoding from MPEG-2 sources with pulldown, such as broadcast television. The x264 commandline app contains some examples of these (such as the common 3:2 pulldown pattern).

  x264 now also exports HRD timing information, which is critical for compliant transport stream muxing. There is currently an active project to write a fully DVB-compatible free software TS muxer that will be able to interface with x264 for a seamless free software broadcast system. It will likely also be possible to repurpose this muxer as part of a free software Blu-ray authoring package.

  All of this is now available in the latest x264.

  http://mirror05.x264.nl/Dark/bluray%20fail.png

• Playing Video on a Sega Dreamcast

  9 mars 2011, par Multimedia Mike — Sega Dreamcast

  Here’s an honest engineering question : If you were tasked to make compressed video play back on a Sega Dreamcast video game console, what video format would you choose ? Personally, I would choose RoQ, the format invented for The 11th Hour computer game and later used in Quake III and other games derived from the same engine. This post explains my reasoning.

  Video Background
  One of the things I wanted to do when I procured a used Sega Dreamcast back in 2001 was turn it into a set-top video playback unit. This is something that a lot of people tried to do, apparently, to varying degrees of success. Interest would wane in a few years as it became easier and easier to crack an Xbox and install XBMC. The Xbox was much better suited to playing codecs that were getting big at the time, most notably MPEG-4 part 2 video (DivX/XviD).

  The Dreamcast, while quite capable when it was released in 1999, was not very well-equipped to deal with an MPEG-type codec. I have recently learned that there are other hackers out there on the internet who are still trying to get the most out of this system. I was contacted for advice about how to make Theora perform better on the Dreamcast.
  
  Interesting thing about consoles and codecs : Since you are necessarily distributing code along with your data, you have far more freedom to use whatever codecs you want for your audio and video data. This is why Vorbis and even Theora have seen quite a bit of use in video games, "internet standards" be darned. Thus, when I realized this application had no hard and fast requirement to use Theora, and that it could use any codec that fit the platform, my mind started churning. When I was programming the DC 10 years ago, I didn’t have access to the same wealth of multimedia knowledge that is currently available.

  Requirements Gathering
  What do we need here ?

  • Codec needs to run on the Sega Dreamcast ; this eliminates codecs for which only binary decoder implementations are available
  • Must decode 320x240 video at 30 fps ; higher resolutions up to 640x480 would be desirable
  • Must deliver decent quality at 12X optical read speeds (DC drive speed)
  • There must be some decent, preferably free, encoder readily available ; speed of encoding, however, is not important ; i.e., "take as long as you need, encoder"

  Theora was the go-to codec because it’s just commonly known as "the free, open source video codec". But clearly it’s not suitable for, well... any purpose, really (sorry, easy target ; OW ! stop throwing things !). VP8/WebM — Theora’s heir apparent — would not qualify either, as my prior experiments have already demonstrated.

  Candidates
  What did the big boys use for video on the Dreamcast ? A lot of games relied on CRI’s Sofdec middleware which was MPEG-1 video and a custom ADPCM format. I don’t know if I have ever seen DC games that used MPEG-1 video at a higher resolution than 320x240 (though I have not searched exhaustively). The fact that CRI used a custom ADPCM format for this application may indicate that there wasn’t enough CPU power left over to decode a perceptual, transform-based audio codec alongside the 320x240 video.

  A few other DC games used 4X Technologies’ 4XM format. The most notable licensee was Alone in the Dark : The New Nightmare (DC version only ; PC version used Bink). This codec was DCT-based but incorporated 16-bit RGB colorspace into its design, presumably to optimize for applications like game consoles that couldn’t directly handle planar YUV. AITD:TNN’s videos were 640x360, a marked improvement over the typical Sofdec fare. I was about to write off 4XM as a contender due to lack of encoder, but the encoding tools are preserved on our samples site. A few other issues, though : The FFmpeg decoder doesn’t seem to work correctly as of this writing (and nobody has noticed yet, even though it’s tested via FATE).

  What ideas do I have ? Right off the bat, I’m thinking vector quantizer (VQ). Vector quantizers are notoriously slow to compress but are blazingly fast to decompress which is why they were popular in the early days of video compression. First, there’s Cinepak. I fear that might be too simple for this application. Plus, I don’t know if existing (binary-only) compressors are very decent. It seems that they only ever had to handle small videos and I’ve heard that they can really fall over if anything more is demanded of them.

  Sorenson Video 1 is another contender. FFmpeg has an encoder (which some allege is better than Sorenson’s original compressor). However, I fear that the wonky algorithm and colorspace might not mesh well with the Dreamcast.

  My thinking quickly converged on RoQ. This was designed to run fullscreen (640x480) video on i486-class hardware. While RoQ fundamentally operates in a YUV colorspace, it’s trivial to convert it to any other colorspace during decoding and the image will be rendered in that colorspace. Plus, there are open source encoders available for the format (namely, several versions of Eric Lasota’s Switchblade encoder, one of which lives natively in FFmpeg), as well as the original proprietary encoder.

  Which Library ?
  There are several code choices here : FFmpeg (LGPL), Switchblade (GPL), and the original Quake 3 source code (GPL). There is one more option that I think might be easiest, which is the decoder Dr. Tim created when he reverse engineered the format in the first place. That has a very liberal "do whatever you like, but be nice and give me credit" license (probably qualifies as BSD).

  This code is no longer at its original home but the Wayback Machine still had a copy, which I have now mirrored (idroq.tar.gz).

  Adaptation
  Dr. Tim’s code still compiles and runs great on Linux (64-bit !) with SDL output. I would like to get it ported to the Dreamcast using the same SDL output, which KallistiOS supports. Then, there is the matter of fixing the longstanding chroma bug in the original sample decoder (described here). The decoder also needs to be modified to natively render RGB565 data, as that will work best with the DC’s graphics hardware.

  After making the code work, I want to profile it and test whether it can handle full-frame 640x480 playback at 30 frames/second. I will need to contrive a sample to achieve this.

  Unfortunately, things went off the rails pretty quickly when I tried to get the RoQ decoder ported to DC/KOS. It looks like there’s a bug in KallistiOS’s minimalistic standard C library, or at least a discrepancy with my desktop Linux system. When you read to the end of a file and then seek backwards to someplace that isn’t the end, is the file still in EOF state ?

  According to my Linux desktop :

  open file ;          feof() = 0
  seek to end ;        feof() = 0
  read one more byte ; feof() = 1
  seek back to start ; feof() = 0
  

  According to KallistiOS :

  open file ;          feof() = 0
  seek to end ;        feof() = 0
  read one more byte ; feof() = 1
  seek back to start ; feof() = 1
  

  Here’s the seek-test.c program I used to test this issue :

  PLAIN TEXT

  C :

  1. #include <stdio .h>
  2.  
  3. int main()
  4. {
  5.   FILE *f ;
  6.   unsigned char byte ;
  7.  
  8.   f = fopen("seek_test.c", "r") ;
  9.   printf("open file ;     feof() = %d\n", feof(f)) ;
  10.   fseek(f, 0, SEEK_END) ;
  11.   printf("seek to end ;    feof() = %d\n", feof(f)) ;
  12.   fread(&byte, 1, 1, f) ;
  13.   printf("read one more byte ; feof() = %d\n", feof(f)) ;
  14.   fseek(f, 0, SEEK_SET) ;
  15.   printf("seek back to start ; feof() = %d\n", feof(f)) ;
  16.   fclose(f) ;
  17.  
  18.   return 0 ;
  19. }

  EOF
  Speaking of EOF, I’m about done for this evening.

  What codec would you select for this task, given the requirements involved ?

• Revision 37444 : Si les theora+vorbis plantent sur vorbis quand ils sont en mono, vorbis ...

  20 avril 2010, par kent1@… — Log

  Si les theora+vorbis plantent sur vorbis quand ils sont en mono, vorbis plantera aussi ... on rationalise tout cela