VLC HowTo/Stream to a website

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Revision as of 01:26, 16 February 2011 by MrGreg (talk | contribs) (minor syntax edit to Appendix)
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This HowTo is intended to be a follow on from Simple_Stream_VLC_to_Website wiki page.


Introduction & Scope

The "Simple Stream VLC to Website" wiki employed an Out of the Box solution with no modifications to the VLC command string. You may wish to read through the previous Wiki first, as it covers fundamentals which are assumed, if you have not done so already. This HowTo is aimed at VLC users who are intending to “Live Stream” from a capture device, eg Webcam, TV camera, live audio source etc and are looking to get a little more out of the features available in VLC and wish to start to understand the command line string and explore techniques to transcode, compress and output a stream to a web site more efficiently and effectively. The following examples are aimed at reducing bandwidth, with a view to streaming on the internet with available upstream bandwidth being the major consideration. The methods described below are targeting a bandwidth of around 235k.

Checks and prerequisites

To start with, Video transcoding, compression and streaming is CPU intensive. So you are going to need something like Intel P4 at 2.4Gb or equivalent as a minimum dedicated box to use the example method 2 in this HowTo. Method 1 is achievable with a pair of 1Gb cpu or more machines. You will have an appreciation of the bandwidth requirements of what you are trying to achieve.



Limitations

This HowTo was written and tested using VLC version series 1.0.1 to 1.1.4 for Win XP.and VLC 0.9.9a to 1.0.6 for Ubuntu Linux. (8.04 & 10.04) Earlier versions may work but have not been tested. This HowTo, the methods and examples have been tested on Operating Systems:

Method 1:-WinXP and Ubuntu Linux (8.04 & 10.04)

Method 2:-WinXP and Ubuntu Linux (8.04 & 10.04)

There are subtle and significant differences in capability and performance of VLC versions and their respective OS platforms. See Notes and Troubleshooting for more information. Hardware capability also plays an important role in this respect.

Web server Apache 2.2 was used in all cases.

Introduction to the VLC Command line

First a couple of reference links for further reading

The above links will give an overview of the commands available to use to manipulate and optimise the Command output string. The following methods and examples modify the generated stream output string. I have included an example of a complete true command line with the same parameters as the Win XP example in Method 2. See Appendix. This should help to give an insight into how to construct a complete command line and enter the appropriate parameters. The following methods and examples deal directly with the output string found in the GUI.

Description of command parameters used in the methods following

vb=xx Video Bandwidth. This parameter in effect sets the target bandwidth of the output video stream and hence the compression required. The more compression the lower the video quality.

ab=xx Audio Bandwidth. As above, but relates to audio.

fps=xx Frames Per Second. The more fps, then the smoother the moving image, however, this uses more bandwidth and compression. So lower fps will give better quality for given bandwidth.

width=xx & height=xx Determines the aspect ratio and the size of the image in pixels. The larger the image, the better the definition, but will require more cpu power and bandwidth. The smaller the image the less compression and bandwidth needed to stream.

deinterlace=<option or none=default> This command useful if you are using an interlaced source. Eg. An NTSC or PAL source

scale=xx determines the output size relative to source size applied to width/height ratio. So scale=0.5 will half original width/height in pixels. Or in this case 25% of the original pixel area.

Transcode Strategies

Single vs Two stage transcode? A single stage transcode may work well for many situations. A two stage transcode may offer advantages in quality at the cost of time and hardware to effect it. A two stage transcode on two different boxes will be less susceptible to quality problems related to mutual or random cpu activity spikes caused by other applications. Method 1 works well with two stage giving an improved picture quality with modest cpu usage given that the wmv codec is less than best compared with what is available. Method 2 can work well in single stage and usually better in two stage, but requires more cpu power.I leave it to you, the user, to experiment with what works best for you.


Tweaking

There are any number of “tweaks” and “mods” that can be applied to the output string or command line. I recommend that you try the example methods as they are before changing everything to suit your anticipated needs. Example tweaks. Look these up in the command line help link.

--sout-keep Keeps your stream open and listening.

--audio-desync=<integer> To preset and synchronise your audio to video, you can +/- the integer.

audio-sync To maintain audio/video synchronisation on the fly. This command will sit inside your sout=#transcode string, Eg after samplerate=xxxxx.

The links referred to above should give a more expansive description of what can be done. Again, do experiment when you have got a working solution.


Method 1 wmv/div3 - asf

For this first method we will keep things very simple. The method is similar to and follows on from “Simple Stream VLC to Website” .There will be a couple of small changes and additions to the default command strings. This method works well with a minimum of effort and hardware. This method is described using wmv and will also work with div3. This method will employ a two stage transcode using two computers. A common configuration. The first stage will be the Primary source/capture/compression (Box1) . The secondary output from (Box2) for final compression and will be your web server.

Box 1 Set up: Select “Streaming” set up your capture devices and set the video size to 256x192 Simply using the default values in the GUI, select “Stream”, then “Next” at source, at “Destinations” check the box “display locally” <optional> , select HTTP from the dropdown box, and click the “Add” button, leave the address field as 0.0.0.0 and change the port number to 8082. Activate transcoding box is checked, select the Windows WMV/asf Transcoding profile and click “next” again. You should now see the “Generated stream output string”. This is where we will make the changes and additions. So. Look at what is in this field and compare with the example below. Then modify the output string with the changes listed below. Or clear the output field and copy and paste.

First output string (box 1) 

:sout=#transcode{vcodec=WMV2,vb=400,fps=15,width=256,height=192,deinterlace,acodec=wma2,ab=64,channels=2,samplerate=44100}:duplicate{dst=std{access=http,mux=asf,dst=0.0.0.0:8081},dst=display}



The changes/additions we have made here:

  1. vb changed to vb=400
  2. Added fps=15
  3. Removed scale=1
  4. Added width=256
  5. Added height=192
  6. I have added “deinterlace” Optional if using an analogue interlaced TV camera
  7. ab changed to ab=64

Box 2 Set up: Pickup the stream from Box 1 with “Open Network Stream” and check that it is streaming OK. Repeat the setup procedure as for Box 1, but use the following output string. Second output string (box 2)

sout=#transcode{vcodec=WMV2,vb=200,fps=15,scale=1,acodec=wma2,ab=32,channels=2}:duplicate{dst=display,dst=std{access=http,mux=asf,dst=0.0.0.0:8082}}


The changes/additions we have made to second output string

1. vb reduced again to 200

2. Added fps=15

3. ab reduced again to 32


Sample metafile for HTML below 


<ASX version ="3.0">
 <TITLE>extstream8082</TITLE>
  <ENTRY>
    <REF HREF="http://youripaddress:8082" />
  </ENTRY>
</ASX>


(saved as <extstream8082.asx>)


Sample HTML for embedded web page 


<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html><head>
<meta content="text/html; charset=ISO-8859-1" http-equiv="content-type"><title>External Stream 8082 embedded</title>

</head>
<body>
<big style="font-weight: bold;"><big>Box 2 streaming
on port 8082<br>
<br>
<br>
</big></big>
<embed src="extstream8082.asx" height="450" width="512">
 </body></html>


Alternatively, you could embed with MS MP.

Method 2 H264 and Flash .flv

Method 2 is somewhat more sophisticated, but should give a good result with minimal bandwidth. It can be successfully effected in a single stage transcode, but a two stage transcode may improve the quality depending on the quality of the hardware available. This method employs an optional first stage pre compression in asf followed by an H264 and a final output in .flv (Flash) and includes a subsection on Flash players “JWPlayer” and “Flowplayer” There is some additional information in Notes further down this HowTo.

Box 1 Set up: (optional) Primary source/capture/compression in asf Select the dropdown box output stream to DIV3/mp3 asf. Follow the similar modifications to the output string as per Method 1, Box 1

The changes/additions we will make here:

  1. vb=600
  2. fps=25
  3. Remove scale=1
  4. Added width=256
  5. Added height=192
  6. I have added “deinterlace” Optional, if using analogue interlaced TV camera
  7. ab changed to ab=64


Box 2 Set up: Secondary output in .flv Select your input, Eg the network stream from Box 1, or your source/capture device. Select Streaming and tab <next> through to the “Options” screen without choosing anything in the previous “Destinations” tab. The “Generated stream output string” field should be blank. The following output strings can be copied and pasted into the empty field. Do make sure that there are no spaces in the string when you copy/paste.

First example string for Win XP (and ffmpeg-x264 enabled Linux) users 

:sout=#transcode{vcodec=h264,vb=200,deinterlace,ab=32,fps=25,width=256,height=192,acodec=mp3,samplerate=44100}:duplicate{dst=std{access=http{mime=video/x-flv},mux=ffmpeg{mux=flv},dst=0.0.0.0:8081/mediaplayer/stream.flv},dst=display}


Second example string for (stripped ffmpeg) Linux users 

:sout=#transcode{vcodec=FLV1,acodec=mp3,vb=200,deinterlace,fps=25,samplerate=44100,ab=32}:duplicate{dst=std{access=http,mux=ffmpeg{mux=flv},dst=192.168.0.42:8081/stream.flv},dst=display}


The above examples should work OK when adapted to your destination IP and port. That said, they are examples of two different approaches. The Windows approach utilises the H264 codec. The Ubuntu Linux approach example provides for a working solution in FLV1 which should work OK with the “Stripped” standard version of ffmpeg in a standard installation. This method would benefit from a two stage transcode to improve quality.

As of Ubuntu 10.04 – VLC 1.0.6 there is a more complete and up to date version of ffmpeg and x264 support in the standard repos'. Eg libavdevice-extra52 & x264. Note VideoLan currently recommends VLC versions 1.1.x . See VideoLan Ubuntu Downloads page for further information

You will probably want to check that everything is working at this stage. So point a VLC client at the stream to check it out. Do note the dst=xx.xx.xx.xx:port/path/stream.flv and check out the “Troubleshooting” section . Next we will need a player to embed the stream into a web page. JWPlayer and Flowplayer are suitable for this purpose. Both of these players need a path to their java files.Eg. The Win XP example had /mediaplayer/ in the path This was the default folder for JWPlayer in that example. The Linux example assumed that the necessary java files placed in the root dir of the webserver and needed no path. These players are described in detail in the documentation on their websites. If you have not used these players before, take time to become familiar with them before using them in this context.

http://flowplayer.org/

http://www.longtailvideo.com/support/tutorials/Embedding-Flash

Example html for a “Flowplayer” embedded page relating to the example VLC Linux output string above. Do note that the Windows example had /mediaplayer/ in the path! This example does not. 


<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html><head><title></title>
<title>This Flash Streaming from VLC video</title>
<script src="flowplayer-3.1.4.min.js"></script><meta content="text/html; charset=ISO-8859-1" http-equiv="content-type">
</head>
<body>
<big style="font-weight: bold;">Flowplayer test file local</big><br>
<br>
<br>
<br>
< See Flowplayer documentation and note below for this line>
</a>
<script language="JavaScript"> flowplayer("player", "flowplayer-3.1.4.swf"); </script>
<p><br>
</body></html>


Note The href= value in this line would contain "http://<yourIP>:8081/stream.flv"

Troubleshooting

OK so it all went wrong? And did not work. At the risk of stating the obvious? Backtrack. Check each stage step by step and prove that each bit is working before moving to the next. Common faults and checks are listed as follows:

  1. 1. The destination address dst=xx.xx.xx.xx can give rise to problems. I have found that Win XP works with dts=0.0.0.0 but Ubuntu linux requires the specific IP of the server Eg 192.168.0.42 or a qualified domain name Eg mywebsite.com.
  1. 2. Many Linux distros may not include by default the full version of ffmpeg and h/x264 and associated libs for encoding. You may need to go research and install all necessary components to get it all working.
  1. 3. The quality of both video and sound can vary due to many factors, which may include the version of VLC, the OS platform, the version of players, plugins Etc. Problems such as stuttering, pixelation, excessive buffering delays are not uncommon. In general terms, keeping up to date with the latest versions of everything is good practice, however in some cases, a newer version may not work as well (if at all) as it’s predecessor.
  1. 4. Realtime streaming is cpu intensive and also sensitive to being interrupted in realtime. Other applications can and will interrupt. Shut down all unnecessary applications ( and the ones in background) Spikes of intensive cpu activity which will not always show up in Task Manager/System Monitor can and will cause problems with the quality of your stream output. You may wish to raise the priority of VLC to reduce the effect of interrupts.
  1. 5 Clients need to be equipped with the necessary means to display your stream! Sounds an obvious statement? Probably not a problem if you have an up to date box, with MS Windows and a recent Flash plugin. I have encountered any number of problems with old hardware, other Operating Systems, browsers and Flash plugins. Don’t be surprised or disappointed at the apparent failure or erratic performance of your stream if you are testing it with a client that is not suitably equipped and able. Using Localhost to check out your stream may also give unexpected and misleading results.


Notes

There are many ways to compress/transcode your stream. The example methods were intended to be a fairly universal and tested starting point. Some combinations work some don’t. Some combinations work in one scenario but will not work in another. If the example methods do not work for you, the Videolan forums are the best place to start looking for a solution.


Appendix

The following is an example of a full command line with the same settings as Method 2 Win XP. The first part, up to ”sout” is the input string. The vdev= and adev= are the (your) input devices and can be viewed and extracted from the first “streaming” window or tab in the GUI, with the “show more options” box checked. You will need to apply the correct syntax for your OS. In Windows ( note the double quotation marks,Eg ”<xxx>” syntax in Windows , for Linux use the single quotation marks '<xxx>') you would enter this at the command prompt path at C:/program files/videolan/vlc . You will also have to add quotation marks around any devices in MS Windows (see example below). Also note, in this example, video size has been defined twice, both in the input and output sections. If you did not include a setting for Video Size in the GUI screen it would not be present in the (generated) input string. Try adding and changing options to see how the VLC GUI builds the input string for you. It is not necessary for video size to be defined here, but should work OK with or without this parameter in the input section. I have included it to show how the string is generated in the GUI. The complete input and output sections can be simply copied and pasted from the GUI into a text editor and built into a complete string to create full working command line. Note, avoid using "word wrap" in the text editor, it can sometimes introduce unwanted characters in the string. 


vlc dshow:// :dshow-vdev="Conexant's BtPCI Capture" :dshow-adev="Aureon 5.1 Fun Wave" :dshow-size="256x192" --sout="#transcode{vcodec=h264,vb=200,deinterlace,fps=25,width=256,height=192,ab=32,acodec=mp3,samplerate=44100}:duplicate{dst=std{access=http{mime=video/x-flv},mux=ffmpeg{mux=flv},dst=0.0.0.0:8081/mediaplayer/stream.flv},dst=display}"
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