Thursday, September 4, 2008

An alpha for python version

Today I'm releasing an alpha version of gstreamer-media-services, which you can test and report possible bugs. Here you can download it, is not so usable, but you can check how is going the project's idea. Just take care with your testing video and audio files, program is not handling overwrite cases!

I've been talking with Stefan and I'll probably change to implement the gstms core ( in C language, to integrate better with gstreamer. I'm just thinking how can I do this, and for now I'm seriously thinking in do it as a gst bin, like decodebin and playbin. I made a diagram of how this could be, profile_diagram, but not sure how could be this XML data profile in sink pad. Probably it's better as a property, but I'm not sure if I can use xml data as gobject property.

Friday, August 22, 2008

A gst bug?

I was trying these last two weeks, while I'm working in UI features, to figure out why sometimes my conversion freezes. I debugged a bit and found that, rarely, if I don't put a time.sleep(1) before playing the pipeline, the pipeline goes to READY state instead of going to PLAYING state. Query goes to position 0, and no error message, neither warning, are sent from bus. If I try to change again to PLAYING state, it stays in READY.

I posted a simple example at , it's based in the example from pygst but I changed to convert to audio and do it 50 times. You can just run it on a terminal with a video as parameter, and check if all 50 videos passed ok. If they pass ok, try sometimes, it's very rarely to happen on this example, as it's a small program, but on gstms is giving many times. I want to know if this bug just happens on my computer or it's a gst bug - or if I'm forgetting something else. BTW, I'm using Ubuntu 8.04 and last stable gstreamer.

If you want to check the alpha version - which I didn't released yet because of this bug - you can download it from svn.

Thursday, August 14, 2008

Trying to release an alpha version

These last two weeks I tried to release a working version of gst-media-services, but I have a unknown bug: sometime, for some type of streams, the pipeline just got paused. I did some things, suggested from IRC community, but it still bugging rarely. The most strange thing on this part is, if I put a time.sleep of 1 second between the gstreamer pipeline linkage and the pipeline play, it works everytime! It's look as sometimes the construction of pipeline isn't being completed, so, has any way of I wait for the pipeline to be complete functional until I set to play state? Ok, I'll spend more time on this these next days.

Also, I want to release an alpha on the Google Summer of Code deadline, August 18th, so, expect something working on my next post. The interface is working ok, and conversion is going rightly, reading elements and constructing pipeline from EncodingProfiles.

Tuesday, July 29, 2008

Continuing Encoding Profiles

Ok, thanks to my previous post comments, I changed the profile XML format. Now I'm not representing the pipeline on itself, but just describing how can be the elements to my program find elements in gstRegistry, and so connect them to construct a pipeline. The good point on this is to possible different elements, so gstms - gst-media-services, this project - can work in different devices, with different elements sets.

But, as nothing is so good, I have some new problems:
  • I need to guess some useful properties - this is needed to basic user interface, as if I show all possible elements properties will turn gstms too hard to use. I'm handling it telling some possible properties, if they don't exist, doesn't matter - let the default value be used. Also, I pretend to change the graphical interface of gstms to advanced mode, so in this mode user can set each property by hand, and here I can just read all possible properties and show on the interface.
  • Connections - how gstms can connect elements in a correct pipeline? I'm not 100% sure about this solution, but I'm only describing each possible-element source, so gstms can search for a element that fits on this source. Also, each possible-element can have, optionally, a tag named recommended-elements which recommends gstms to elements in gst that can be used. I'm not so sure about video conversions, I need to build one first.
  • audioconvert, ffmpegcolorspace - these two elements are always used in audio and video conversion, to change raw audio and raw video formats. But, is there any other element like this? Can I search automatically for them, with possibly another name? I didn't solve it.
Also, I'm fearing that gstms find some element which, for some unknown reason, doesn't work for a conversion. So, in this case, how can I handle it? And what about elements that are not encoders, like id3v2mux, how can I search for a possible element like this?

For who want to know how is going the xml format, here a link to websvn of google project. Please, comment, community opinions have being very useful to the project!

Saturday, July 19, 2008

Starting Encoding Profiles

Two weeks without reporting, but here I am. I spent this time with implementing the proposed interface, which I did all in glade format and I can easily edit it. Also, the project is detecting format - oh, I spent some hours implementing my own pipeline with decodebin to get info from files in the input and just later I found gst.extend.discoverer... ok, now I have more experience with pipelines, and I'm working in the xml format - I really don't know for now how can I represent the pipelines for themselves, as they need some processing power. For an example, to encode to mp3 I can use id3mux or id3v2mux, but to choose one I need to tell to try each. I saw the method of Banshee, using S-expression, is very useful but I would like to use only XML, just not sure exactly how.

A way that I was thinking is like:
<element id="audioconvert" type="required">
<element id="lame" type="required">
<property id="bitrate" type="optional">
<property id="vbr" type="">
<if expression="vbr!=0"> <!-- vbr!=0 need to use html encoded chars -->
<if expression="vbr != 0">
<element id="xingmux" type="optional">
<element id="id3v2mux" type="optional">
<if expression="exist(id3v2mux)">
<element id="id3v2mux" type="optional">
<elif expression="exist(id3mux)">
<element id="id3mux type=">


update: I corrected the XML code which was not appearing.

Sunday, July 6, 2008

A dialog proposal for conversions

I made a simple UI dialog for gst-media-services, as the following (and at the wiki):

  • Files to convert: is a list that user can add or remove files with the right-side buttons, where user can add any number of files to input them. I'm not sure if that way is understandable to the user that he can choose many files to do a batch operation or he can choose audio and/or video and/or images to mix them. When a file is added, the list can have the properties on it to set properties of the mix (like in what time it should be shown, for how much time if is a image, what is it volume if is a sound, and so on). Not intented to be released at a first time, the input could be a stream or an URI address, considering any stream too.

  • Video Output: here user (or the application which uses this dialog) choose the video format, based in the Encoding Profiles. Each profile has some properties, which is under discussion at the EncodingProfiles section. The default option depends of the input, the selected files: If user choose only audio files, the video appears as "No Video" (better is to disable it). If he choose a video, this box goes to a "maintain the same format" option, considering that there weren't any application which called the dialog with a format input. If user choose many videos, the dialog counts how much videos have of each format and the major format is the selected, so user can convert the minority videos to the majority format. If user choose videos and images, audios and videos, audios videos and images together, or just images, it's a mix case and dialog can handle this by showing some advanced options for each file selected.

  • Audio Output: default is to let the same audio. When user choose a video format, the audio choose the video-audio's profile, as I'm planning that all videos links audio profiles for its audio part. A "No Audio" option need to be done too.

  • Target folder: Where the results should be dropped. - problem with the mix operation: how can I presume what is the name of resulting file? Should I add another field for it if I detect a mix case?

  • Bottom Buttons: Edit profiles is a button to open the Profiles Editor, a tool that I want to do later, to help users to build their own profiles. At least, this button can let the user build its own pipeline, or change a pre-defined one. Transcode button transcode the files (is it the best name? Should I use Convert / Extract / Mix depending of selected operation?), and appear two new buttons when the operation is finished: "Close" and "Open target". A progress screen should appear when the transcode button is pressed.

I think I'll not change very much this dialog, and my wish is to offer this to applications to use it. I didn't cover some use cases yet, like when dialog do conversions or to just return the Gstreamer pipeline to the application which is calling gst-media-services. I'm already implementing the basic functions for the dialog, but I need to work in a XML parser for EncodingProfiles too.
Any suggestions, just drop in comments!

Monday, June 23, 2008

Desired transcode operations

I'm inviting everyone to help with the desired transcode operations, what operations of conversion, extraction and merging of videos, audios and why not images do you want to do easily, or you already do but not so easily. Here at the project wiki you can just use the template to fill with your operations. This can contribute to I see what Gstreamer can offer (with my gst-registry read, previous post) and what people want to do. And if you hate wikis you can email me or just comment here at the blog and I put at the wiki!
I also created a space at google code where you all can track my work of transcoder application, and redesigned the wiki. I also didn't so much in this last week because of some exams, and I have some this week too so I want to collect information to the application too, while I'll design some possible UI dialogs for the project. The idea of these dialogs is to offer them as a part of gst-media-services to all applications, so a great challenge on this is how to make them usable by different apps. Suggestions are welcome.

Tuesday, June 10, 2008

Reading from Gst Registry

This last week I worked to read info from GstRegistry. This info should help the EncodingProfiles list of possible formats to convert, and also, as commented in my previous post from Laszlo, this could help on recognizing mimetypes supported too.

It was not hard to read plugins and their features - as these all are very well documented in Gstreamer docs, I just lost some time searching the "get_possible_dynamic_pad_templates". The possible dynamic pads templates are included in the static templates... So I read their pads templates and caps, then I just need to parse them in somehow to it help in building profiles list. Parsing registry is needed too to check if plugins from each transcode operation are available.

With registry parsed, now comes the question: How it could help to build the list? A way that I'm thinking on is to rank the features by their caps mimetypes which each one can generate, and then somehow put them in XML list to help others to compose each transcode operation. Another way is to just build a table with these info, allowing re-ordering and filtering according to each feature details. Ideas?

Tuesday, June 3, 2008

Encoding Profiles

Reporting my GSoC work, last week I worked in the encoding profiles idea (, deriving it from Banshee's Audio Profile, which is a very nice profile system for transcoding audio files. I'm putting at my project wiki all issues that I'm having to create an example XML of this generalized media profile, which supports video, audio and, why not, images later. With this profile I hope to ease user creation of any kind of transcode operation, according to its need or to an application need.

I'm also comparing some transcoder applications at my project wiki too. If you know any other open source application that I didn't cited at wiki, please just leave a comment there to I analyze it and check if I can get anything to help me on my project!

Now this week I'll delay Encoding Profiles to do, as a Stefan's suggestion, a python script to dump possible configurations for codecs and themselves from registry, so any example script that does something like this is welcome too!

Saturday, May 3, 2008

Hello world

This is a hello world post, where I want to say hello to all gst community! I am one of accepted students to work in Google Summer of Code with the project Media services to transcode video and audio in different formats, and want to make a great project, which is intended to help users and applications, offering them services to transcode videos and sounds with gstreamer.

For who is interested in more details, check the wiki design at Gstreamer Wiki. This blog is intended to report what I'm doing during my (winter) summer, so please contribute with suggestions always, as I'm here to learn with everyone. Oh, and vote for what is the best name of this project, in this blog poll, I don't like MediaTrans too much.