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• 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 ?

• Diamond Rio Artifacts

  30 août 2012, par Multimedia Mike — Multimedia History

  Remember the Diamond Rio PMP300 ? It’s credited with being the very first portable MP3 player, released all the way back in 1998 (I say ‘credited’ because I visited an audio museum once which exhibited a Toshiba MP3 player from 1997). I recently rescued a pristine set of Rio artifacts from a recycle pile.

  
  
  

  I wondered if I should scan the manual for posterity. However, a Google search indicates that a proper PDF (loaded with pleas to not illegally copy music) isn’t very difficult to come by. Here are the other items that came with the unit :

  
  
  Click for larger image
  

  Ah, more memories (of dialup internet) : A tie-in with another Diamond product, this time a modem which claims to enable the user to download songs at up to 112 kilobits per second. I wonder if that was really possible. I remember that 56k modems were a stretch and 33.6k was the best that most users could hope for.

  There is also a separate piece of paper that advises the buyer that the parallel port adapter might look a bit different than what is seen in the printed copy. Imagine the age of downloading to your MP3 player via parallel port while pulling down new songs via dialup internet.

  The artifacts also included not one, but two CD-ROMs :

  
  
  Click for larger image
  

  One is a driver and software disc, so no big surprise there. The other has a selection of MP3 files for your shiny new MP3 player. I’m wondering if these should be proactively preserved. I was going to process the files’ metadata and publish it here, for the benefit of search engines. However, while metadata is present, the files don’t conform to any metadata format that FFmpeg/Libav recognize. The files mention Brava Software Inc. in their metadata sections. Still, individual filenames at the end of this post.

  Leftovers :
  A few other miscellaneous multimedia acquisitions :

  
  
  

  I still want to study all of these old multimedia creation programs in depth some day. Theatrix Hollywood is a creative writing game, Wikipedia alleges (I’m a bit rigid with my exact definition of what constitutes a game). Here is an example movie output from this software. Meanwhile, the Mad Dog Multimedia CD-ROM apparently came packaged with a 56X CD-ROM drive (roughly the pinnacle of CD-ROM speeds). I found it has some version of Sonic Foundry’s ACID software, thus making good on the “applications” claim on the CD-ROM copy.

  Diamond Rio MP3 Sampler
  These are the names of the MP3 files found on the Diamond Rio MP3 sampler for the benefit of search engines.

  13_days.mp3
  albert_einstein_dreams.mp3
  a_man_of_many_colours.mp3
  anything_for_love.mp3
  a_secret_place.mp3
  bake_sale.mp3
  bigger_than_the_both_of_us.mp3
  boogie_beat.mp3
  bring_it_on.mp3
  buskersoundcheck_hippo.mp3
  charm.mp3
  chemical_disturbance.mp3
  coastin.mp3
  credit_is_due.mp3
  dance_again.mp3
  destiny.mp3
  dig_a_little_deeper.mp3
  diplomat6_bigmouthshut.mp3
  dirty_littlemonster.mp3
  dirty.mp3
  drivin.mp3
  Eric_Clapton_Last_Train.mp3
  etude_in_c_sharp_minor_op_42_n.mp3
  everybody_here.mp3
  freedom_4_all.mp3
  grandpas_advice.mp3
  groove.mp3
  heartland.mp3
  he_loved_her_so.mp3
  highway_to_hell.mp3
  hit_the_ground_runnin.mp3
  i_feel_fine_today.mp3
  im_not_lost_im_exploring.mp3
  into_the_void.mp3
  its_alright.mp3
  i_will_be_there.mp3
  i_will_pass_this_way_again.mp3
  juiceboxwilly_hepcat.mp3
  just_an_illusion.mp3
  keepin_time_by_the_river.mp3
  king_of_the_brooklyn_delta.mp3
  lovermilou_ringingbell.mp3
  middle_aged_rock_and_rollers.mp3
  midnight_high.mp3
  mr_schwinn.mp3
  my_brilliant_masterpiece.mp3
  my_gallery.mp3
  on_the_river_road.mp3
  pouring_rain.mp3
  prayer.mp3
  rats_in_my_bedroom.mp3
  razor_serpent_and_the_dub_mix.mp3
  ruthbuzzy_pleasestophangin.mp3
  secret_love.mp3
  ships.mp3
  silence_the_thunder.mp3
  sleeping_beauty.mp3
  slow_burn.mp3
  standing_in_my_own_way.mp3
  take_no_prisoners.mp3
  takin_up_space.mp3
  Taylor_Dayne_Unstoppable.mp3
  the_laundromat_song.mp3
  the_old_dun_cow.mp3
  the_people_i_meet.mp3
  trip_trigger_avenue.mp3
  tru-luv.mp3
  unfortunate_man.mp3
  vertigo.mp3
  when_she_runs.mp3
  where_do_we_go_from_here.mp3
  words_of_earnest.mp3
  

• End of Piwik Mobile 1 – Focus is on Piwik Mobile 2

  2 septembre 2014, par Piwik Core Team — Community, Piwik Mobile Releases

  More than four years after its initial release, we will remove Piwik Mobile 1 from the Apple App Store and Google Play Store in one week. During that time the app was downloaded more than 60.000 times with an average rating of 4.6 and over 2000 ratings. Thank you to our community of users for all of this !

  Why we must focus on Piwik Mobile 2

  Unfortunately we do not have the resources to maintain Piwik Mobile 1 to be compatible with the latest iOS and Android updates (namely iOS 8 and Android L). The last update of Piwik Mobile 1 was over one year ago and the underlying framework, which we are using to develop the app, is nearly two years old. Making the code compatible with the current version of the underlying framework to support the latest platform versions would take us many weeks. As a little background : From the beginning Piwik Mobile 1 has been a free app and was developed by a single person Thomas in his spare time who is now focussing on Piwik Mobile 2.

  Can I still get it ?

  We are announcing this today so you get a chance to install the app via the Apple App Store and Google Play Store while it is still available.

  If you are one of the 87% of our Piwik Mobile 1 users who are already using Android 4+ or iOS 7+ then you can install Piwik Mobile 2 (make sure you upgrade your Piwik platform to 1.12 or 2.x recommended).

  What happens after the app is removed ?

  If you have already installed the app it won’t be removed from your device and you will still be able to use it. Android users can still download Piwik Mobile 1 but we cannot guarantee it will work on all devices. Lastly the code our free software is available on GitHub and you can build it from the source if you have to.

  The future of Piwik Mobile

  Piwik Mobile version 2.1 is currently in beta testing phase. This new version includes several useful new features such as support for Segmentation. If you use Android, give it a try !