Official Kodi Wiki - User contributions [en]

Archive:Google Summer of Code/2015

2015-03-03T09:53:03Z

Montellese: added "UPnP ContentDirectory implementation using OhNet" proposal

{{mininav| [[Google Summer of Code]] }}
[[File:GSOC_2015_logo-blog.jpg‎|left|200px]]Welcome to the Kodi [http://www.google-melange.com/gsoc/homepage/google/gsoc2015 Google Summer of Code] ideas page. 

We encourage interested students to review some of the ideas on this page, and then feel free to provide input on any ideas you may have in the '''[http://forum.kodi.tv/forumdisplay.php?fid=220 Kodi GSoC subforum]''' and chat about any project you’d love to cover. To propose a project, see '''[[#Students project proposal ideas]]'''.

From '''16 March''' to '''27 March''', any interested students may apply at the [http://www.google-melange.com/gsoc/homepage/google/gsoc2015 GSOC home page] to work with Kodi. After that, we’ll notify applicants whether we get to work with each other according to the [http://www.google-melange.com/gsoc/events/google/gsoc2015 GSOC schedule].
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== About Us ==
As there may be many students who have landed here as a result of GSOC, but are unfamiliar with the project, here are a few resources that may help explain what we are about.

:Kodi (formerly known as XBMC) is an award-winning free and open source (GPL) software media player and entertainment hub for digital media, designed around the 10-foot interface (living room) environment. Created in 2003 by a group of like minded programmers, Kodi is a non-profit project run and developed by volunteers located around the world. More than 500 software developers have contributed to Kodi, and 100-plus translators have worked to expand its reach, making it available in more than 60 languages. For more information, see the page '''[[Kodi]]'''.

<br />
To get an idea of what Kodi is truly capable of, it really must be seen. Check out a few other user-created videos:<br />
[http://www.youtube.com/watch?v=NcogPuSo-DU Kodi with the default Confluence skin]<br />
[http://www.youtube.com/watch?v=4asUCtE0ONU Kodi with Aeon Nox skin]<br />
[http://www.youtube.com/watch?v=4NR57ELY28s Kodi on Raspberry Pi]<br />
[http://www.youtube.com/watch?v=e_0PB5hfz_k Kodi's new PVR functionality]<br />
<br />

Kodi is written primarily in c++ and runs on a variety of platforms including Android, iOS, Linux, OS X, and Windows. It has been ported to work on several low-power platforms including the Raspberry Pi and Android.

Kodi was a mentoring organization in [[Google Summer of Code 2008|2008]], [[Google Summer of Code 2012|2012]] and [[Google Summer of Code 2013|2013]], and had team members involved in GSoC for other projects during 2011.

If Kodi is selected as a mentoring organization for 2015, students will need to review the Overview of a good project proposal, follow the outline for proposals when applying, and review the list of project ideas detailed below. Students are welcome to propose ideas outside the list and are encouraged to be as creative as they like.

=== Mentors ===
All mentors and backup mentors are extremely experienced in the Kodi codebase and will thus be able to assist students in getting to know the codebase and in quickly identifying projects that are both achievable for someone unfamiliar with the internal workings of Kodi and desirable to the wider Kodi community.

== Project Proposals ==
=== Overview ===
Qualifications for a good Summer of Code proposal:
* Discrete, well-defined, modular
* Comprised of a series of measurable sub-goals
* Based on open specs that are available free of charge
* Based on complete specs
An example of a good proposal is the implementation of a new feature or function that is not yet available in Kodi.

An example of a less desirable proposal is one that's not as measurable, such as refactoring an existing API. Bad proposals tend to be ones that would require touching a lot of core code.

To re-iterate:
* Localized/isolated code projects = ''good''
* Global code refactoring = ''bad''
* A project should have a set of subgoals, so even if the end goal turns out to be too big some of the parts will be of benefit.
* Not too big! This is an important problem when choosing a project, while it is fun to think about solving a grand project its not always realistic. Its better to finish a smaller project than to start a grand one.

=== Outline for proposals ===
{{divbox|blue||
PROJECT TITLE GOES HERE

* '''Name:'''
* '''forum/e-mail:'''
* '''Summary:''' A somewhat small but explanatory walk through of the project. It should not be overly detailed just enough to understand the problem trying to be fixed and how this project opt to solve it.
* '''How will I achieve this:''' Explain how the project will be done, what technologies are needed and how to implement them.
* '''What will the project focus on:''' Explain what the project will focus on, what is the important parts of the project.
* '''Benefits:''' Who will benefit and why from this project. Think about what a user or developer may need or do to benefit from it. Why does it benefit many users.
* '''Goals:''' What is the goal of the project, a project may not always solve the problem entirely as it may take to much time. Think hard about what can be accomplished during a summer with your skill and deduct that quite a bit. If the project can't be done after this perhaps its better to opt for a smaller one or one with subgoals.
* '''What does it touch in Kodi:''' Think about what parts of the code this may touch, Kodi is a big application and a lot of the code is spread out and very complex. If a project touches to much it may be impossible to complete.
* '''Requirements:''' What is needed to complete the project, what code language knowledge what hardware etc.
* '''Possible mentors:''' Place to add possible mentors (Team-Kodi will add this).
}}

== Team-Kodi proposal ideas up for discussion ==

=== Server Improvement ===

====Transcoding====
*Transcoding is already supported in a number of other open source projects and FFMPEG. Additionally, limited audio transcoding is available in Kodi right now. However to fully support the wide range of devices out there, not to mention better support file transfers on low memory devices, Kodi needs to fully support audio and video transcoding.

====UPnP Improvements including File Transfers====
*Support downloading of of media items (the actual file not just the metadata) from another Kodi instance (e.g. through UPnP) into the local library. This could be done in a "send to" way and in a "download" way and it could also be combined with transcoding depending on the target device.
*UPnP device profiles. there's already a PR that goes in that direction and the problem is that right now we can only really provide device specific MIME type hacks but if we have transcoding we'll definitely need this

====UPnP ContentDirectory implementation using OhNet====
[http://www.openhome.org/wiki/OhNet OhNet] is a cross-platform UPnP stack provided by the [http://www.openhome.org/wiki/Oh:Overview OpenHome] project and contains basic interfaces/implementations for all objects and resources defined in most of the UPnP specifications with an addition of OpenHome specific stuff which improves playlist handling and other things not properly covered by any UPnP specification.
Kodi relies on the [http://sourceforge.net/projects/platinum/ Platinum UPnP SDK] which has very limited possibilities to extend the existing functionality. Furthermore any extensions fixes need to be coded into code not maintained by Team Kodi. Therefore moving to a different UPnP implementation that provides a similar feature set but can be easily extended would have a high benefit for Kodi.

The main goal is to develop a [http://www.upnp.org/specs/av/UPnP-av-ContentDirectory-v4-Service-20101231.pdf UPnP ContentDirectory] implementation using the OhNet UPnP stack (see https://github.com/Montellese/xbmc/commit/a0596372c6398e1bbf7fb0534ad21d510604d2f8 for a start) either inside or separate of Kodi that supports most of the features specified in the UPnP ContentDirectory specification. An additional goal would be to make it easily extensible (think UPnP profiles and vendor-specific properties) without having to touch the actual implementation.

=== Better Profile Support ===
Profile support inside Kodi remains extremely hacked together. Improving profile projects would likely be broken down into smaller chunks to make each chunk truly achieveable in a summer.

===Web Browser in Kodi===
Initial work on Web Browser implementation already exists, but much is left to do on this project, and many developers are excited to help act as a mentor for this particular project.

===Gaming in Kodi ===
====Retroplayer====
*Developer Garbear has broken down the Retroplayer project into manageable pieces including input, core, game addons, peripheral addons, netplay, a game library implementation, and shaders to do things like emulate a CRT monitor. Any one of these pieces could make an excellent summer project depending on your familiarity in the area.
====NVIDIA Gamestream in Kodi====
*Limelight is a GPL licensed project that runs on a variety of platforms and is primarily written in java that should be relatively easily integrated into the Kodi file system, allowing for any device running Kodi with access to a controller or a keyboard and mouse to launch and play any game or application being served on a local PC with a relatively recent NVIDIA graphics card.

=== More ===
We feel it is important to note that, while we are interested in a focus on the listed three areas, we would like to stress passion, expertise, and creativity above all else. If you would like to do something completely different, definitely send in that proposal. The ideas listed above are, as always, merely suggestions. We will be interested in any idea, so long as you can communicate your interest, your background, and your solution the problem.

== Students project proposal ideas ==

Submit your own proposals on the '''[http://forum.kodi.tv/forumdisplay.php?fid=220 Kodi GSOC 2015 forum]'''. They can be as big or as small as you feel you can comfortably accomplish between '''25 May''' and '''21 August'''. In the end, it's better to have a smaller, completed project, rather than a larger, incomplete project.

To submit a proposal idea:
# Copy the text from '''[[#Outline for proposals]]'''.
# Create a new forum post '''[http://forum.kodi.tv/forumdisplay.php?fid=220 here]''' and paste the text.
# Fill out everything using your specific proposal.

[[Category:Google Summer of Code]]

Audio troubleshooting

2014-07-31T06:43:26Z

Montellese: Typo

{{mininav|[[Audio]]{{l2|[[Troubleshooting]]}} }}

<section begin="intro" />This page describes some of the steps you can take to troubleshoot audio problem and gives background information on audio concepts as a foundation for understand why some things work as they do.<section end="intro" />

=Background=
To understand how XBMC processes audio you must first have a basic understanding of how audio in the digital domain works. This page will help guide you to understanding some basics in audio and how to troubleshoot basic audio issues.

==Pulse Code Modulation (PCM)==
When analog audio is converted into the digital domain the near universal format used is Pulse Code Modulation (PCM). All manipulation of audio in the digital domain is always done on audio in the PCM format, therefore functions in XBMC such as volume control can only be done on PCM data, therefore if audio is in one of the Encoded Formats XBMC must decode the audio to PCM in order to manipulate it for volume control.

===Number of Channels===
When number of channels is referred to, it will nearly always be the number of PCM channels that is meant. Since PCM is uncompressed audio this is a frequently used way of expressing the raw bandwidth for a particular audio path, thus when you see the "Number of channels" setting in XBMC this is the number of PCM channels.

==Encoded Formats==
There are two types of encoded formats, these are lossy and lossless.

===Lossy===
These formats take the PCM audio data and use encoding algorithms to throw away (hence term lossy) audio information that the human ear cannot hear in order to save space. Examples of lossy formats:
* Dolby Digital AC3
* DTS

====Why 5.1 is possible when number of channels is 2.0?====
When audio is in a lossy format it is so much smaller than the original uncompressed PCM data that it's still possible to send 5.1 channels even when "Number of channels" is 2.0.

Take SPDIF as an example, this type of audio path can only handle a maximum of 2 PCM channels, however a format such as DTS can still be passed as 5.1 channels because once encoded into DTS the data is so much smaller than what is required for 2 PCM channels.

===Lossless===
These formats differ from the Lossy formats in that they don't chuck data away but instead compressed the PCM data with highly sophisticated algorithms that allow the original audio to be reconstructed (hence lossless), this is very similar in principle to the way zip & rar works on documents in that the original source can always be reconstructed.
Examples of Lossless formats:
*DTS-HD MA
*Dolby TrueHD
*Flac

For the lossless formats such as DTS=HD MA, although the audio data is compressed the they still require the same number of PCM channels to be available as they are trying to pass unlike the lossy formats so 7.1 channel DTS-HD MA still requires 7.1 PCM channels.

====DTS-HD MA====
DTS High Definition Master Audio (DTS-HD MA) is the commonly used on Blu-ray and uses a Core plus Extension encoding scheme where:

* '''Core -''' is a lossy DTS stream encoded as 5.1.
* '''Extension -''' is the additional data required for the audio to be lossless including a possible further 2 channels for a 7.1 audio stream.

The advantage of this type of encoding scheme is that equipment that can't decode the full DTS-HD MA will still be able to recognise the lossy Core DTS 5.1 stream. Thus in XBMC if you deselect the DTS-HD option if using HDMI, or you are using SPDIF so that option is not available, then you will get DTS 5.1 out.

* '''Pro -''' compatible with all equipment which supports DTS
* '''Con -''' can be larger than other formats

====Dolby TrueHD====
TrueHD is another commonly used Blu-ray audio format, however in this case it's a single lossless audio stream so tends to be slightly smaller than DTS-HD MA, however if you have a single TrueHD audio track for your video then all equipment must be capable of decoding it. It you have a mixture of equipment where some can decode Dolby TrueHD and some can only decode Dolby Digital, then 2 audio tracks are required, one containing the Dolby TrueHD audio upto 7.1 channels and one containing Dolby Digital upto 5.1 channels, however having 2 audio tracks will likely negate any space saving over DTS-HD MA.

* '''Pro -''' can be smaller data size than other lossless formats
* '''Con -''' equipment must be compatible with the format

==What this means for XBMC?==
XBMC has three modes of operation:

* '''Passthrough -''' This is where encoded audio types such as DTS are sent by XBMC for decoding elsewhere, typically a AVR, however the device the encoded audio is being sent to MUST be able to decode the audio format e.g. DTS.
* '''Decode -''' This is where the audio is decoded into PCM, this can be used where a format such as DTS can't be sent in it's encoded format so instead the audio is decoded into PCM.
* '''Transcode -''' This is used where multichannel audio needs to sent over a connection that only has 2 PCM channels, XBMC does this by encoding the 5.1 audio into AC3 5.1.

=Troubleshooting (WIP)=
This is currently a Work In Progress
==No Audio or Video Stutters==

This generally indicates you are trying to pass a format that is not compatible with your hardware.

===Check volume===
If audio type is PCM then volume needs to be checked. Check that mute is not on with the mute toggle {{keypress|F8}} and also make sure volume is at maximum with {{keypress|+}}.

===Check passthrough formats===
If you have the passthrough option available and it is enabled, then try disabling all the passthrough encoded audio formats such as Dolby Digital. If this fixes the problem then your system is not working with one of the passthrough types, there are then two things you can do:

* Check files with '''''[http://mediaarea.net/en/MediaInfo MediaInfo]''''' to see what type of audio they contain.
* Enable each format one at a time and test a file with that type of audio to see if a problem is encountered.
* Look the the xbmc.log file, refer to '''''[[log_file]]''''' for how to find this and enable debug loging, and towards the start you should see all the audio devices listed with it's properties.

====Interpret Log====

In the log file all valid audio devices installed will be listed, when looking at the log the two important bits of information are lines '''<nowiki>m_channels</nowiki>''' and '''<nowiki>m_dataFormats</nowiki>'''.

* '''<nowiki>m_channels</nowiki> -''' this is the number of PCM channels, if HD audio such as DTS-HD is required then 8 channels must be shown here. For example:
::<code>m_channels: FL,FR,FC,LFE,SL,SR,BL,BR</code>
* '''<nowiki>m_dataFormats</nowiki> -''' this is the formats the audio device supports, for example:
::<code>m_dataFormats: AE_FMT_DTSHD,AE_FMT_TRUEHD,AE_FMT_EAC3,AE_FMT_DTS,AE_FMT_AC3,AE_FMT_S24NE4,AE_FMT_S24LE4,AE_FMT_S24BE4,AE_FMT_S16NE,AE_FMT_S16LE,AE_FMT_S16BE,AE_FMT_LPCM</code>
::where
::<code>AE_FMT_DTSHD</code> = DTS-HD
::<code>AE_FMT_TRUEHD</code> = TrueHD
::<code>AE_FMT_EAC3</code> = Dolby Digital Plus
::<code>AE_FMT_DTS</code> = DTS
::<code>AE_FMT_AC3</code> = Dolby Digital
::<code>AE_FMT_S*</code> = PCM where * is different for each PCM data type e.g. <code>AE_FMT_S24NE4</code>

== No HD Audio==
DTS-HD and TrueHD are not shown in the XBMC settings.

In order to pass HD audio there are several things required:

*The HDMI device that supports HD audio e.g. PC graphic card with HDMI port. {{Note|You cannot pass HD audio over SPDIF.}}
*If a PC the software on the device including any drivers must also support HD audio.
*The HDMI receiving device must support HD audio e.g. AVR.
*The two connected devices must be able to successfully communicate their capabilities with one another via EDID/ELD.{{Note|Configuration of features such as HDMI CEC can affect the information contained in the EDID/ELD.}}

[[Category:Audio]]
[[Category:Troubleshooting]]
{{Gotham updated}}