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• MPEG-DASH - Multiplexed Representations Issue

  26 avril 2017, par Mike

  I’m trying to learn ffmpeg, MP4Box, and MPEG-DASH, but I’m running into an issue with the .mp4 I’m using. I’m using ffmpeg to demux the mp4 with this command :

  ffmpeg -i test.mp4 -c:v copy -g 72 -an video.mp4 -c:a copy audio.mp4

  Once the two files are created, I use MP4Box to segment the files for the dash player using this command :

  MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ output.mp4

  Which does create all the files I think I need. Then I point the player to the output_dash.mpd and nothing happens except a ton of messages in the console :

  [8] EME detected on this user agent! (ProtectionModel_21Jan2015) 
  
  [11] Playback Initialized 
  
  [21] [dash.js 2.3.0] MediaPlayer has been initialized 
  
  [64] Parsing complete: ( xml2json: 3.42ms, objectiron: 2.61ms, total: 0.00603s) 
  
  [65] Manifest has been refreshed at Wed Apr 12 2017 12:16:52 GMT-0600 (MDT)[1492021012.196]  
  
  [72] MediaSource attached to element.  Waiting on open... 
  
  [77] MediaSource is open! 
  
  [77] Duration successfully set to: 148.34 
  
  [78] Added 0 inline events 
  
  [78] No video data. 
  
  [79] No audio data. 
  
  [79] No text data. 
  
  [79] No fragmentedText data. 
  
  [79] No embeddedText data. 
  
  [80] Multiplexed representations are intentionally not supported, as they are not compliant with the DASH-AVC/264 guidelines 
  
  [81] No streams to play.

  Here is the MP4Box -info on the video I’m using :

  * Movie Info *
  
      Timescale 1000 - Duration 00:02:28.336
  
      Fragmented File no - 2 track(s)
  
      File suitable for progressive download (moov before mdat)
  
      File Brand mp42 - version 512
  
      Created: GMT Wed Feb  6 06:28:16 2036
  
  
  
  File has root IOD (9 bytes)
  
  Scene PL 0xff - Graphics PL 0xff - OD PL 0xff
  
  Visual PL: Not part of MPEG-4 Visual profiles (0xfe)
  
  Audio PL: Not part of MPEG-4 audio profiles (0xfe)
  
  No streams included in root OD
  
  
  
  iTunes Info:
  
      Name: Rogue One - A Star Wars Story
  
      Artist: Lucasfilm
  
      Genre: Trailer
  
      Created: 2016
  
      Encoder Software: HandBrake 0.10.2 2015060900
  
      Cover Art: JPEG File
  
  
  
  Track # 1 Info - TrackID 1 - TimeScale 90000 - Duration 00:02:28.335
  
  Media Info: Language "Undetermined" - Type "vide:avc1" - 3552 samples
  
  Visual Track layout: x=0 y=0 width=1920 height=816
  
  MPEG-4 Config: Visual Stream - ObjectTypeIndication 0x21
  
  AVC/H264 Video - Visual Size 1920 x 816
  
      AVC Info: 1 SPS - 1 PPS - Profile High @ Level 4.1
  
      NAL Unit length bits: 32
  
      Pixel Aspect Ratio 1:1 - Indicated track size 1920 x 816
  
  Self-synchronized
  
  
  
  Track # 2 Info - TrackID 2 - TimeScale 44100 - Duration 00:02:28.305
  
  Media Info: Language "English" - Type "soun:mp4a" - 6387 samples
  
  MPEG-4 Config: Audio Stream - ObjectTypeIndication 0x40
  
  MPEG-4 Audio MPEG-4 Audio AAC LC - 2 Channel(s) - SampleRate 44100
  
  Synchronized on stream 1
  
  Alternate Group ID 1

  I know I need to separate the video and audio and I think that’s where my issue is. The command I’m using probably isn’t doing the right thing.

  Is there a better command to demux my mp4 ?
  Is the MP4Box command I’m using best for segmenting the files ?
  If I use different files, will they always need to be demuxed ?

  One thing to mention, if I use the following commands everything works fine, but there is no audio because of the -an which means it’s only video :

  ffmpeg -i test.mp4 -c:v copy -g 72 -an output.mp4
  
  
  
  MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ output.mp4

  UPDATE

  I noticed that the video had no audio stream, but the audio had the video stream which is why I got the mux error. I thought that might be an issue so I ran this command to keep the unwanted streams out of the outputs :

  ffmpeg -i test.mp4 -c:v copy -g 72 -an video.mp4 -c:a copy -vn audio.mp4

  then I run :

  MP4Box -dash 4000 -frag 1000 -rap -segment-name segment_ video.mp4 audio.mp4

  now I no longer get the Multiplexed representations are intentionally not supported... message, but now I get :

  [122] Video Element Error: MEDIA_ERR_SRC_NOT_SUPPORTED 
  
  [123] [object MediaError] 
  
  [125] Schedule controller stopping for audio 
  
  [126] Caught pending play exception - continuing (NotSupportedError: Failed to load because no supported source was found.)

  I tried playing the video and audio independently through Chrome and they both work, just not through the dash player. Ugh, this is painful to learn, but I feel like I’m making progress.

• How to contribute to open source, for companies

  18 octobre 2010, par Dark Shikari — development, open source, x264

  I have seen many nigh-incomprehensible attempts by companies to contribute to open source projects, including x264. Developers are often simply boggled, wondering why the companies seem incapable of proper communication. The companies assume the developers are being unreceptive, while the developers assume the companies are being incompetent, idiotic, or malicious. Most of this seems to boil down to a basic lack of understanding of how open source works, resulting in a wide variety of misunderstandings. Accordingly, this post will cover the dos and don’ts of corporate contribution to open source.

  Do : contact the project using their preferred medium of communication.

  Most open source projects use public methods of communication, such as mailing lists and IRC. It’s not the end of the world if you mistakenly make contact with the wrong people or via the wrong medium, but be prepared to switch to the correct one once informed ! You may not be experienced using whatever form of communication the project uses, but if you refuse to communicate through proper channels, they will likely not be as inclined to assist you. Larger open source projects are often much like companies in that they have different parts to their organization with different roles. Don’t assume that everyone is a major developer !

  If you don’t know what to do, a good bet is often to just ask someone.

  Don’t : contact only one person.

  Open source projects are a communal effort. Major contributions are looked over by multiple developers and are often discussed by the community as a whole. Yet many companies tend to contact only a single person in lieu of dealing with the project proper. This has many flaws : to begin with, it forces a single developer (who isn’t paid by you) to act as your liaison, adding yet another layer between what you want and the people you want to talk to. Contribution to open source projects should not be a game of telephone.

  Of course, there are exceptions to this : sometimes a single developer is in charge of the entirety of some particular aspect of a project that you intend to contribute to, in which case this might not be so bad.

  Do : make clear exactly what it is you are contributing.

  Are you contributing code ? Development resources ? Money ? API documentation ? Make it as clear as possible, from the start ! How developers react, which developers get involved, and their expectations will depend heavily on what they think you are providing. Make sure their expectations match reality. Great confusion can result when they do not.

  This also applies in the reverse — if there’s something you need from the project, such as support or assistance with development of your patch, make that explicitly clear.

  Don’t : code dump.

  Code does not have intrinsic value : it is only useful as part of a working, living project. Most projects react very negatively to large “dumps” of code without associated human resources. That is, they expect you to work with them to finalize the code until it is ready to be committed. Of course, it’s better to work with the project from the start : this avoids the situation of writing 50,000 lines of code independently and then finding that half of it needs to be rewritten. Or, worse, writing an enormous amount of code only to find it completely unnecessary.

  Of course, the reverse option — keeping such code to yourself — is often even more costly, as it forces you to maintain the code instead of the official developers.

  Do : ignore trolls.

  As mentioned above, many projects use public communication methods — which, of course, allow anyone to communicate, by nature of being public. Not everyone on a project’s IRC or mailing list is necessarily qualified to officially represent the project. It is not too uncommon for a prospective corporate contributor to be turned off by the uninviting words of someone who isn’t even involved in the project due to assuming that they were. Make sure you’re dealing with the right people before making conclusions.

  Don’t : disappear.

  If you are going to try to be involved in a project, you need to stay in contact. We’ve had all too many companies who simply disappear after the initial introduction. Some tell us that we’ll need an NDA, then never provide it or send status updates. You may know why you’re not in contact — political issues at the company, product launch crunches, a nice vacation to the Bahamas — but we don’t ! If you disappear, we will assume that you gave up.

  Above all, don’t assume that being at a large successful company makes you immune to these problems. If anything, these problems seem to be the most common at the largest companies. I didn’t name any names in this post, but practically every single one of these rules has been violated at some point by companies looking to contribute to x264. In the larger scale of open source, these problems happen constantly. Don’t fall into the same traps that many other companies have.

  If you’re an open source developer reading this post, remember it next time you see a company acting seemingly nonsensically in an attempt to contribute : it’s quite possible they just don’t know what to do. And just because they’re doing it wrong doesn’t mean that it isn’t your responsibility to try to help them do it right.

• Presentation of Piwik’s collaborative translations platform : oTrance [Interview]

  19 avril 2013, par matt — Community, translation

  Piwik enables domain administrators, hobbyists, power users, personal website builders and everyone in between to access enormous amounts of data for website analytics. To support all those users, Piwik needs to be available in a number of different languages. From the start, we made internationalization (i18n) part of Piwik’s DNA. There are now dozens active volunteers who help make sure each language is well represented in the latest official release of Piwik. As of now, Piwik is available in 48 languages.

  Recently a new tool became available that makes the translation of Piwik much easier. The software we are using is an open source platform called oTrance. It has made our translation architecture more robust, and it allows us to expedite the timely delivery of high quality and up-to-date translations to the thousands of people who rely on Piwik every day.

  We’ve met with oTrance creator and lead developer Daniel Schlichtholz who answered a few questions for us.

  1. What is oTrance ?
  2. What sets oTrance apart from the other ways to manage translations ?
  3. Now that oTranCe 1.0 is out, what will you be working on next ?

  What is oTrance ?

  oTranCe is the short form of “Online Translation Center”. It was born because I needed a translation platform for my project MySQLDumper.

  Many languages have been added by the community and manual maintenance became more and more time consuming. I wanted to change that. So I searched for an existing platform I could use and tested a lot of approaches. To put a long story short : none of the given solutions satisfied my needs.

  From the view of a translator maintaining a language should be as easy as possible. In most cases they have to install a program on their local machine or the workflow was too difficult. A translator doesn’t want to struggle with technical things ; he just wants to translate the phrases and wants to know the progress.

  That’s the main goal we want to reach : to make the translation process as easy as possible.

  What sets oTrance apart from the other ways to manage translations ?

  Ease of use is one advantage of oTranCe compared to other solutions. Another advantage is that project administrators can install oTranCe on their own server – so nobody is dependant of a third party provider.

  We love to get feedback from other users. User feedback influences the way oTranCe is developed. We believe that this way oTranCe satisfies the requirements of the real world.

  We also have extensive user documentation, in our “Working with oTranCe” wiki. We try to document use cases in an understandable way. We don’t write down marketing buzz words, but try to explain the use from the view of the user/administrator.

  Now that oTranCe 1.0 is out, what will you be working on next ?

  The language files can be exported to version control and oTranCe can commit changes to the target repository. Currently we support export to Subversion, and we are working on a Git export adapter, which will be released soon.

  Another issue we are trying to solve is the context problem. When your project uses many different phrases the translator often doesn’t know in which context the current phrase is used. Version 1.1.0 (not released yet, but you can grab the latest developer version from GitHub) introduces the oTranCe-connector. The idea behind it : a small plug in grabs the used phrases/keys on the current page, and on click this list is submitted to oTranCe, where the translator can edit the words. This way the translator knows in which context these phrases are used. I wrote a small plug in for OXID eShop. Since it is really easy to implement, my hope is that other plug ins for other applications will be added by the community.

  Matthieu : Congratulations Daniel for having created such an awesome Translation Platform. At Piwik we are really thankful for oTranCe, which has resulted in much better translation process, and happier translators. Keep up the good work !

  If you are a Piwik user, and if you want to participate in translating Piwik, please sign up for an account on oTrance and become part of the team making Piwik available in more languages across the world.