Here’s the tricky part. As we know from the exec() man page this function executes the given command. As described there, the exact declaration of this method is:

string exec  ( string $command  [, array &$output  [, int &$return_var  ]] )

So far so good. Normally exec() will return the output of the command.

FFmpeg version SVN-r21880, Copyright (c) 2000-2010 Fabrice Bellard, et al.
  built on Feb 18 2010 15:53:28 with gcc 4.3.2
  configuration: --enable-gpl --enable-nonfree --enable-shared --enable-postproc --enable-avfilter --enable-avfilter-lavf --enable-pthreads --enable-x11grab --enable-bzlib --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-version3 --enable-libdc1394 --enable-libfaac --enable-libfaad --enable-libfaadbin --enable-libgsm --enable-libmp3lame --enable-libschroedinger --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-zlib --prefix=/usr/local
  libavutil     50. 9. 0 / 50. 9. 0
  libavcodec    52.54. 0 / 52.54. 0
  libavformat   52.52. 0 / 52.52. 0
  libavdevice   52. 2. 0 / 52. 2. 0
  libavfilter    1.17. 0 /  1.17. 0
  libswscale     0.10. 0 /  0.10. 0
  libpostproc   51. 2. 0 / 51. 2. 0
...

However sometimes that is not so true. Let’s see an example with the popular FFMPEG program. In one hand when you try to start a video converting program with PHP you can simply call exec with the FFMPEG command as the first parameter. The output is OK and you can dump it as in the example here.

echo exec('/usr/local/bin/ffmpeg -i input.mp4 -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -vpre normal -threads 0 output.mp4', $output);	
var_dump($output);

In some cases you can call FFMPEG only with the -i option to get some info about the input file. Such info can be the size of the image, the bitrate of the source file or the length of the movie. Executing this command:

echo exec('/usr/local/bin/ffmpeg -i input.mp4', $output);	
var_dump($output);

in the terminal you’ll see the output you wish. However if you trying to execute the command via exec() the output remains empty?

Why the Output Parameter is Empty?

Looking at the terminal screen you can’t see the difference, but actually in the second case, when you execute FFMPEG only with the -i option, the output is redirected to the standard error output. That’s why you can’t see it in the exec() second parameter. However there is a solution.

Solution and Conclusion

The solution is quite simple. You’ve to redirect the output of the FFMPEG command to the standard output.

/usr/local/bin/ffmpeg -i /var/www/android/test.mp4 2>&1

Now you can call this line with exec().

echo exec('/usr/local/bin/ffmpeg -i input.mp4 2>&1', $output);	
var_dump($output);

This showcase with the FFMPEG is important not only because now you can call FFMPEG’s command without problems, but because you now know that exec() can’t read the standard error output. Thus you’ve to be careful and always redirect to the standard output.

The Problem

There is only one problem – I still cannot find easily the section of the site in TinyMCE. So I’m supposed to click on the comment’s link. This is a pity and perhaps that’s why I couldn’t find it before. Moxiecode should make this section more accessible!

Most of the mobile devices today support GPS geo tagging. In fact most of them come bundled with navigation software that uses GPS and therefore all the pictures and (maybe) videos can be geo tagged. But as expected different vendors come with different support and formats.

iPhone OS comes with geotagging both on video and image files, while the latest Android and Symbian (the Nokia main OS for smartphones) can geo tag only images.

Even more – until recently Symbian didn’t support any geotagging before the installation of an additional software – such as Location Tagger . So generally the things are quite simple:

1. iPhone OS geotags both video and image files;
2. Android geotags only images;
3. Symbian geotags only images – and on some devices this is possible only after installing a software;

This is in breve the state of mobile device geotagging!

Why Use GPS Data?

Perhaps one of the main reasons why not support geotagging especially on video files can be the usage of those geo tags. First of all what a geotag means?





You may know that even Android doesn’t “geotag” videos this is not quite true. Because after using you gallery you can see where those videos are shot. This is fantastic, but actually the real information about where the video has been taken is not into the video file, but it’s in an additional log file that keeps it. Thus actually the video files doesn’t know the geo coordinates.

Here comes the problem with video format, because you cannot be sure that every format supports tags that can keep geo coordinates. Actually quicktime’s MOV can store them, while Symbian’s 3GP cannot. In fact Symbian cannot store any geo information about video files!

So now we’ve at least three different formats for each of those three vendors.

1. quicktime for iPhone
2. mpeg-4 with Android
3. 3gp with Symbian

For now I can only say that iPhone can keep the geotag into his video files.





But let me return to the question – why we need this geo tags? Until the video file is on the mobile device – there’s no problem. But once you try to download it – whether on Flickr, YouTube, Picasa, etc. you’ll lose any geo information if it’s not into the file tags. And of course if the above sites can’t read it!

The general reason to store this data into the file is to move it along with the file. Once you move this file from your mobile device to a web platform you’ll see where the file has been created.

EXIF, Exiftool and PHP’s exif_read_data

There are several tools to read geotags. For images, and here we talk only for JPEGs, this is the EXIF information. You can download the exif command line program and try to reed data with it:

exif filename.jpg

Which can result in something like that:

Manufacturer        |Nokia                                                     
Model               |E71                                                       
Orientation         |top - left                                                
x-Resolution        |300.00                                                    
y-Resolution        |300.00                                                    
Resolution Unit     |Inch                                                      
YCbCr Positioning   |centered                                                  
Compression         |JPEG compression                                          
x-Resolution        |72.00                                                     
y-Resolution        |72.00                                                     
Resolution Unit     |Inch                                                      
FNumber             |f/3.2                                                     
Exif Version        |Exif Version 2.2                                          
Date and Time (origi|2011:01:24 12:15:01                                       
Date and Time (digit|2011:01:24 12:15:01                                       
ComponentsConfigurat|Y Cb Cr -                                                 
Aperture            |3.20 EV (f/3.0)                                           
Light Source        |0                                                         
Flash               |Flash did not fire, auto mode.                            
Focal Length        |4.9 mm                                                    
FlashPixVersion     |FlashPix Version 1.0                                      
Color Space         |sRGB                                                      
PixelXDimension     |2048                                                      
PixelYDimension     |1536                                                      
Custom Rendered     |Normal process                                            
Exposure Mode       |Auto exposure                                             
White Balance       |Auto white balance                                        
Digital Zoom Ratio  |1.00                                                      
Scene Capture Type  |Standard                                                  
GPS tag version     |0x02, 0x02, 0x00, 0x00                                    
North or South Latit|N                                                         
Latitude            |42.00, 39.00, 24.67                                       
East or West Longitu|E                                                         
Longitude           |23.00, 21.00, 28.45                                       
Altitude reference  |0x00                                                      
Altitude            |625.50 

While for video files (iPhone) exif cannot help you, this is possible through Exiftool. With it you can read even iPhone video geotags:

./exiftool filname.mov

In addition this information can be read with PHP via exif_read_data:

$info = exif_read_data('filename.jpg');
var_dump($info);

And this will give you not only standard tags, but geo tags too.

It’s really full of video sharing websites out there, but in fact almost all of them use Flash player to display their video files. This is the reality now, but with the coming of HTML5, perhaps the things are changing a bit!

First of all if you start dealing with video sharing platforms the first thing to do maybe is to find a good Flash (.flv) player and to convert all your video content in FLV.

Few things to know with Flash video players:

1. The user can play those videos only after installing the Flash Plugin to his browser;
2. The video must be encoded either in FLV (or FLash Video) or in MPEG-4 with h.264 codec. Only than the Flash player can play it;

The HTML5, which can be described as variety of new “things” in the HTML comes with a native <video> tag. Something like the <img> tag where you can just point the source of the image in the src attribute.

First Question – How Does it Look Like?

To get more fluent with the <video> tag you must simply thing of it as a “complex” <img> tag. You just point to the video and the browser will do the rest. To be more exact let me send you to the w3schools page, but the important thing as they say:

Until now, there has never been a standard for showing video on a web page.

However to start from somewhere here’s a little snippet showing you the basic, but very basic usage of the HTML5 video tag:

<video src="path_to_the_video" controls="controls"></video>

Second Question – Is Every Video Playable?

But of course not! There are different browser – different video formats. Currently there are three formats, supported by the different browsers.

1. H.264
2. VP8
3. Theora

Note that these are video codecs and a video files does not consists of only a video codec, but also of an audio codec. This makes the video file a container of several things. As you may know already H.264 is used with MPEG-4 video format, which results in .mp4 extended files, Theora is used in OGG, which are all those .ogg files out in the web, and finaly VP8 is used in WebM … or in .webm videos.

First thing to know FLV files (.flv) can also be encoded with H.264. Actually Flash player has a h.264 decoder so this makes it possible to play both .mp4 and .flv files encoded with H.264.

Second thing to notice – where are those .webm files? I’ve never seen them!

Third Question – What is WebM and VP8?

Behind WebM and VP8 is Google. This is a new video format based again on Theora. Actually it pretends to be as good in compressing as H.264, which by the way is meant to be the best. But let me take a look at Nettuts+:

VP8, a relatively new codec, is the brainchild of On2 — the same guys behind Theora. Google acquired On2 in 2010, and opened up all the underlying patents for the codec into the public domain.

WebM, the container of choice for most current browsers, utilizes VP8 for compressing its video content and Vorbis for its audio. It produces content similar in quality to H.264.

It is completely royalty free, now and for the future. On the downside, though, it has limited hardware decoding support as well as third party device/mobile support.

Final Question – How Can I Convert a Video in WebM?

This answer is given by this article, where as it is said after having the ffmpeg version >= 0.6 you simply can use this command:

ffmpeg -i girltalk.mp4 -f webm -vcodec libvpx -acodec libvorbis -aq 90 -ac 2 girltalk.webm

Conclusion

It’s interesting to see what will happen one day. There is going to be either a harmonious life in the web video field or the codecs/formats will be as much as the browser? Who knows?

However FFMPEG is a converting program and many things depend on what kind of video files come as an input and what do you want to achieve as an output. Here comes the codec question, where various libraries can help. In my case, as I wrote few posts ago, I use MP4 as output encoded with h.264, both encoded with ffmpeg/libx264. So far so good, but there is one main problem that anyone used this pair knows.

Flash Player and MP4

As far as I know Flash Player 9 and beyond plays video files encoded with MP4/h.264 except the typical FLV (flash video files). This can help video sites not only to share their video content via web – within browser based flash players, but also to show them via some mobile device interface where MP4/h.264 is perhaps the only one reasonable solution. In this case the file is accessible in both medias.

By default Flash Player can play such FFMPEG encoded .mp4 files, but fist the whole file must be downloaded by the browser and only than the playback can begin. That’s because the FFMPEG puts meta info at the end of the video file, while the flash player needs it at the beginning and only than to begin playing while the file is still downloading.

qt-faststart

As the name of this software says this program helps you move the important meta info from the end to the beginning of the file. This helps the video to playback as early as possible. In an ideal circumstances everything works just fine, but there is a serious problem in fact.

qt-faststart and Server Crash

qt-faststart is responsible to move the meta info where it must be – at the beginning of the video file, but cannot finish execution when the video file is broken or the meta info doesn’t exists. Actually this is not a problem of qt-faststart, but to the video file. However this was a critical problem in my case, because the video files remains stuck for hours of execution and 99% of CPU usage.

Thankfully there is a solution and it can be found in the qt-faststart wrapper – qtfaststart.py

qtfaststart.py

written on Python this script overcomes the disadvantages of qt-faststart. As described by his author Daniel G. Taylor:

Works everywhere Python can be installed

Handles both 32-bit (stco) and 64-bit (co64) atoms

Handles any file where the mdat atom is before the moov atom

Preserves the order of other atoms

Can replace the original file (if given no output file)

With its help not only qt-faststart doesn’t crash, but also the video files remain progressive as desired. The installation process is as difficult as copy/paste on the server where Python must be installed.

Now the problem is that this comes with very large list of options, which are difficult to setup, especially for newbies like me. Than everything’s difficult, once because the resulting quality is not always the same as the input file’s quality.

The Solution

Is to use presets. Thankfully ffmpeg with libx264 can be used with presets, i.e. NORMAL, HD etc. which means that you don’t have to setup a command by hand and the resulting quality is the same as the input quality.

Here’s a sample command using normal preset:

ffmpeg -i source.mp4 -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -vpre normal -threads 0 -crf 22 output.mp4

here the source can be either mp4 or some other file format as FLV for instance.

Yes it may sound strange, but now with the upcoming HTML5 features every browser again is playing its own game. Firefox and Opera support only OGG Theora, Chrome and Safari only MP4 and what about IE .. it doesn’t support anything. Than why should we convert to mp4 with h.264 codec?

Because everybody is playing flash

And that’s again very sad but at least the flash players are playing mp4 with this encoding, which is good because this file will be playable under most of the mobiles. And if you have a large video site to support why don’t you convert to mp4 and play it with a Flash Player and give the opportunity to play mp4 on mobile.

Only one file under the sky

Thus you gain to keep only one file – playable under every device?

YouTube and FLV

Now I wonder why YouTube have both FLV and MP4 formats?

Of course if you’d like to be perfect …

Convert every video to MP4, FLV and OGG, but that means 3 files for every video?!