&gt; **H.264** is a new standard for video compression which has more advanced 
&gt; compression methods than the basic **MPEG-4** compression. One of the 
&gt; advantages of H.264 is the high compression rate. It is about 1.5 to 2
&gt; times  more efficient than MPEG-4 encoding. This high compression rate
&gt; makes it  possible to record more information on the same hard disk.  
&gt; The image quality is also better and playback is more fluent than with
&gt; basic  MPEG-4 compression.  The most interesting feature however is
&gt; the lower bit-rate required for network  transmission.  
&gt; **So the 3 main advantages of H.264 over MPEG-4 compression are:**  
&gt; ‐ Small file size for longer recording time and better network transmission.  
&gt; ‐ Fluent and better video quality for real time playback  
&gt; ‐ More efficient mobile surveillance application
&gt;
&gt; H264 is now enshrined in MPEG4 as part 10 also known as AVC

**Refer to: [http://www.velleman.eu/downloads/3/h264_vs_mpeg4_en.pdf][1]**

Hope this helps.


  [1]: http://www.velleman.eu/downloads/3/h264_vs_mpeg4_en.pdf

They are names for the same standard from two different industries with different naming methods, the guys who make &amp; sell movies and the guys who transfer the movies over the internet. Since 2003: &quot;MPEG 4 Part 10&quot; = &quot;H.264&quot; = &quot;AVC&quot;.
Before that the relationship was a little looser in that they are not equal but an &quot;**MPEG 4 Part 2**&quot; decoder can render a stream that&#39;s **&quot;H.263&quot;**.
The Next standard is &quot;**MPEG H Part 2**&quot; = &quot;**H.265**&quot; = &quot;HEVC&quot;

I have a simple .net command line tool written and compiled under Windows, using .net 3.5SP1.  I would like to run it on Linux using Mono.

I am using Ubuntu 12.04, and installed Mono Runtime using the Ubuntu software center.  If I try to start my app in the terminal by doing:

    mono MyApp.exe

I get the error:
&gt; The assembly mscorlib.dll was not found or could not be loaded.  It should have been installed in the &#39;usr/lib/mono/2.0/mscorlib.dll&#39;.

If I navigate to that location, I see that it does not exist.  However, there is `usr/lib/mono/4.0/mscorlib.dll` (and some more DLLs in the same folder).

So seemingly there is a version mismatch.

[in case it matters, `mono -V` shows `Mono JIT compiler version 2.10.8.1 (Debia 2.10.8.1-1ubuntu2)` ]

Unable to run .net app with Mono - mscorlib.dll not found (version mismatch?)

There are situations where it can be useful to get the exact pixel width of an `em` measurement.  For example, suppose you have an element with a CSS property (like border or padding) which is measured in ems, and you need to get the exact pixel width of the border or padding.  There&#39;s an existing question which touches on this topic:

https://stackoverflow.com/questions/1442542/how-can-i-get-default-font-size-in-pixels-by-using-javascript-or-jquery

This question is asking about getting the *default font size* - which is necessary in order to convert a relative `em` value to an exact `px` value.  

[This answer][1] has a pretty good explanation of how to go about getting the default font size of an element:

&gt; Since ems measure width you can always compute the exact pixel font
&gt; size by creating a div that is 1000 ems long and dividing its
&gt; client-Width property by 1000. I seem to recall ems are truncated to
&gt; the nearest thousandth, so you need 1000 ems to avoid an erroneous
&gt; truncation of the pixel result.

So, using this answer as a guide, I wrote the following function to get the default font size:

    function getDefaultFontSize(parentElement)
    {
    	parentElement = parentElement || document.body;
    	var div = document.createElement(&#39;div&#39;);
    	div.style.width = &quot;1000em&quot;;
    	parentElement.appendChild(div);
      	var pixels = div.offsetWidth / 1000;
    	parentElement.removeChild(div);
    	return pixels;
    }

Once you have the default font size, you can convert any `em` width to `px` width by just multiplying the ems by the element&#39;s default font size and rounding the result:

`Math.round(ems * getDefaultFontSize(element.parentNode))`

**Problem:** The `getDefaultFontSize` is ideally supposed to be a simple, side-effect free function that returns the default font size.  But it *DOES* have an unfortunate side effect: it modifies the DOM!  It appends a child and then removes the child. Appending the child is necessary in order to get a valid `offsetWidth` property.  If you don&#39;t append the child `div` to the DOM, the `offsetWidth` property remains at 0 because the element is never rendered.  Even though we immediately remove the child element, this function can still create unintended side effects, such as firing an event (like Internet Explorer&#39;s `onpropertychange` or W3C&#39;s `DOMSubtreeModified` event) that was listening on the parent element. 

**Question:** Is there any way to write a truly side-effect free `getDefaultFontSize()` function that won&#39;t accidentally fire event handlers or cause other unintended side effects?


  [1]: https://stackoverflow.com/a/4530334/168288

Converting em to px in Javascript (and getting default font size)

Are these both the same? Is H.264 codec of MPEG-4? What if I need to convert flv to high definition H.264 video format? I want make online tv streaming and want to use PHP or Python.

What is the difference between H.264 video and MPEG-4 video?

<p>Are these both the same? Is H.264 codec of MPEG-4? What if I need to convert flv to high definition H.264 video format? I want make online tv streaming and want to use PHP or Python.</p>


I just started blogging using jekyll. I write my posts in markdown. Now,  I want to include a youtube video in my post. How can I do this?

Also, I dont really like the pygments highlighting provided by jekyll by default. Is there anyway I can change  this to some other style? If yes, can you point me to some nice styles/plugins? 

how to include video in jekyll markdown blog

In the documentation of Android [TextureView](http://developer.android.com/reference/android/view/TextureView.html) it says that you can use a TextureView to play video: 
But I cant seem to find any example of how to do this. Does anyone know? 

I need to use a `textureView` because I want to animate the video. I want to play a video in .3gp/.mp4 format, not video from the Camera :)

Any help would be appreciated..


UPDATE:

Solution is posted as a community wiki answer


Playing video on TextureView

I am currently using these commands:

    Top left corner
    ffmpeg –i inputvideo.avi -vf &quot;movie=watermarklogo.png [watermark]; [in][watermark] overlay=10:10 [out]&quot; outputvideo.flv
    
    Top right corner
    ffmpeg –i inputvideo.avi -vf &quot;movie=watermarklogo.png [watermark]; [in][watermark] overlay=main_w-overlay_w-10:10 [out]&quot; outputvideo.flv
    
    Bottom left corner
    ffmpeg –i inputvideo.avi -vf &quot;movie=watermarklogo.png [watermark]; [in][watermark] overlay=10:main_h-overlay_h-10 [out]&quot; outputvideo.flv
    
    Bottom right corner
    ffmpeg –i inputvideo.avi -vf &quot;movie=watermarklogo.png [watermark]; [in][watermark] overlay=(main_w-overlay_w-10)/2:(main_h-overlay_h-10)/2 [out]&quot; outputvideo.flv

How to place watermark center of the video ?

How to add transparent watermark in center of a video with ffmpeg?

Hi I need to extract frames from videos using ffmpeg.. Is there a faster way to do it than this:

    ffmpeg -i file.mpg -r 1/1 $filename%03d.jpg

?

Fastest way to extract frames using ffmpeg?

I have an app that allows a user to record a video with `UIImagePickerController` and then upload it to YouTube. The problem is that the video file that `UIImagePickerController` creates is HUGE, even when the video is only 5 seconds long. For example, a 5 second long video is 16-20 megabytes. I want to keep the video in 540 or 720 quality, but I want to reduce the file size.

I&#39;ve been experimenting with AVFoundation and `AVAssetExportSession` to try to get a smaller file size. I&#39;ve tried the following code:

    AVAsset *video = [AVAsset assetWithURL:videoURL];
    AVAssetExportSession *exportSession = [AVAssetExportSession exportSessionWithAsset:video presetName:AVAssetExportPresetPassthrough];
    exportSession.shouldOptimizeForNetworkUse = YES;
    exportSession.outputFileType = AVFileTypeMPEG4;
    exportSession.outputURL = [pathToSavedVideosDirectory URLByAppendingPathComponent:@&quot;vid1.mp4&quot;];
    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        NSLog(@&quot;done processing video!&quot;);
    }];

But **this hasn&#39;t reduced the file size at all**. I know what I&#39;m doing is possible because in Apple&#39;s Photos app, when you select **&quot;share on YouTube&quot;**, will automatically process the video file so its small enough to upload. I want to do the same thing in my app. 

How can I accomplish this?

How can I reduce the file size of a video created with UIImagePickerController?

I am trying to encode a .mp4 video from a set of frames using FFMPEG using the libx264 codec.

This is the command I am running:

    /usr/local/bin/ffmpeg -r 24 -i frame_%05d.jpg -vcodec libx264 -y -an video.mp4

I sometimes get the following error:

    [libx264 @ 0xa3b85a0] height not divisible by 2 (520x369)

After searching around a bit it seems that the issue has something to do with the scaling algorithm and can be fixed by adding a -vf argument. 

However, in my case I don&#39;t want to do any scaling. Ideally, I want to keep the dimensions exactly the same as the frames. Any advice? Is there some sort of aspect ratio that h264 enforces?

FFMPEG (libx264) &quot;height not divisible by 2&quot;

I&#39;m working on a H.264 Decoder and I&#39;m wondering where to find the SPS and PPS. My reference literature tells me that those are NAL Units encoded in the H.264-Stream, but when I look into an example-MP4-File with IsoViewer, it says that the SPS and PPS are in the avcC Box. 

How exactly does this work? How does it look for .mkv files or other H.264 containers?

Possible Locations for Sequence/Picture Parameter Set(s) for H.264 Stream

I had a lot of trouble figuring out how to use Apple&#39;s Hardware accelerated video framework to decompress an H.264 video stream.  After a few weeks I figured it out and wanted to share an extensive example since I couldn&#39;t find one.

My goal is to give a thorough, instructive example of Video Toolbox introduced in [WWDC &#39;14 session 513][1].  My code will not compile or run since it needs to be integrated with an elementary H.264 stream (like a video read from a file or streamed from online etc) and needs to be tweaked depending on the specific case.  

I should mention that I have very little experience with video en/decoding except what I learned while googling the subject.  I don&#39;t know all the details about video formats, parameter structure etc. so I&#39;ve only included what I think you need to know.

I am using XCode 6.2 and have deployed to iOS devices that are running iOS 8.1 and 8.2.

  [1]: https://developer.apple.com/videos/wwdc/2014/#513

How to use VideoToolbox to decompress H.264 video stream

I&#39;m looking for a way to rotate videos shot with my Nexus 4 on my Debian Wheezy sytem. The videos are shot in portrait mode and I would like to rotate them to landscape mode. Preferably the rotation is command-line driven.

I have found several previous questions which are hinting at a good solution but I can&#39;t seem to manage to get it working.

To begin with there was this question:
https://stackoverflow.com/questions/3937387/rotating-videos-with-ffmpeg

But it indicates that ffmpeg is outdated and that I should use avconv. I found this question detailing the way to go forward.
https://askubuntu.com/questions/269429/how-can-i-rotate-video-by-180-degrees-with-avconv

This made me using following command:

    avconv -i original.mp4 -vf &quot;transpose=1&quot; -codec:v libx264 -preset slow -crf 25 -codec:a copy flipped.mp4

However, this is painstakingly slow (last test took me more than 6 hours for less than 3 minutes of footage) and does not result in a playable movie. I also get an error in logging output which states Mb Rate &gt; level limit.

Is there an issue here with the re-encoding? Should I first re-encode the videos from my phone to another, more &quot;workable&quot; encoding before applying the rotations? Or am I missing another important point?

Rotate mp4 videos without re-encoding

I&#39;ve been struggling with this issue for more than a week, and most likely it is a bug in the **Qualcomm GPU/hardware video encoder**. Since we are pressed to release the application, and their developer forums did not provide any feedback, I am posting it here too, hoping that someone is able to provide some clues, or even better, a workaround so that the bug in the encoder is not triggered.
 
The application encodes from a Surface. When certain images are rendered to the surface, the encoder fails (100%) in the same place (when the frame currently being encoded is a key frame). The Logcat output from the encoder at the point of the crash is(with the last lines repeated at a very high rate):

    11-26 11:41:33.312: E/OMX-VENC-720p(25949): ERROR: async_msg_process() - Error statuscode = 1
    11-26 11:41:33.312: E/ACodec(29317): [OMX.qcom.video.encoder.avc] ERROR(0x80001009)
    11-26 11:41:33.312: E/MediaCodec(29317): Codec reported an error. (omx error 0x80001009, internalError -2147483648)
    11-26 11:41:33.362: E/OMX-VENC-720p(25949): ERROR: venc_use_buf:set input buffer failed 
    11-26 11:41:33.362: E/OMX-VENC-720p(25949): ERROR: in dev_use_buf
    11-26 11:41:33.362: E/OMX-VENC-720p(25949): ERROR: empty_buffer_done() failed!
    11-26 11:41:33.372: E/OMX-VENC-720p(25949): m_fbd_count at o/p flush = 306
    11-26 11:41:33.372: E/OMX-VENC-720p(25949): m_etb_count at i/p flush = 313
    11-26 11:41:33.372: E/OMX-VENC-720p(25949): ERROR: ioctl VEN_IOCTL_CMD_FILL_OUTPUT_BUFFER failed
    11-26 11:41:33.372: E/OMX-VENC-720p(25949): ERROR: dev_fill_buf() Failed
    11-26 11:41:33.372: E/OMX-VENC-720p(25949): ERROR: FTBProxy() failed!

I can replicate it also on [Grafika][1] by simply replacing in the _Record GL app_ the drawing of two geometric forms with drawing one of the problematic images, full screen, in landscape mode, and changing the bitrate to a higher value (7Mbps).
The crash of the encoder happens sooner for larger bitrate.

Here is one [image][2] that seems to break it easily and here is [RecordFBOActivity.java][3] with the required changes. 

With Grafika, I tested and the encoder crashes on both Samsung S4, international version, and on the original Nexus 4. With our software, which is a little more complex than rendering the plain image, it still crashes on both. Did not test on any other Adreno devices. On Samsung S3, with a Mali 400 GPU, it works fine.

At 4Mbps, the encoder in our application still crashes on both S4 and N4, but later. Grafika crashes on N4 in the same place, but not on S4.

EDIT: According to comments bellow, it can be reproduced also when encoding the same image from the buffer. Various tests seem to narrow the conditions to reproduce it at: h264 hw encoder on Qualcomm devices, encoding a still image for many frames (this determines very low bitrates in the encoder due to similar frames), error appearing while encoding a key frame (the error appears only when encoding certain images, which seem to have more detail, i.e. need many bits for intra coding).


  [1]: https://github.com/google/grafika
  [2]: http://turl.ca/tqzs
  [3]: http://pastebin.com/gYXn5UWa

Encoder crash on Adreno GPU while encoding from Surface

Situation:
----------
I am trying to export video with some parameters like video bit rate, audio bit rate, frame rate, changing video resolution, etc. Note that I am letting the user set the video frame rate in fractions; like user can set the video frame rate say, 23.98.

I use **AVAssetWriter** and **AVAssetReader** for this operation. I use [AVAssetWriterInputPixelBufferAdaptor][1] for writing the sample buffers.

Everything else works just fine, except the **video frame rate**.


What I have tried:
------------------

 1. Setting the **AVAssetWriter.movieTimeScale** as suggested [here][2]. Which does change the video frame rate but also makes the video sluggish. ([gist here][3])

----------
 2. Setting **AVVideoExpectedSourceFrameRateKey**. Which does not help. ([gist here][4])

----------
 3. Setting **AVAssetWriterInput.mediaTimeScale**. Again, it changes the video frame rate but makes the video sluggish as *AVAssetWriter.movieTimeScale* does. The video shows different frames at some point and sometimes it sticks and resumes again. ([gist here][5])

----------
 4. Using **AVAssetReaderVideoCompositionOutput** and setting **AVMutableVideoComposition.frameDuration**; just like [SDAVAssetExportSession][6] does. Ironically with SDAVAssetExportSession code, the video is being exported just at the right frame rate that I want, but it just does not work in my code. [gist here][7]

I am not sure why it won&#39;t work with my code. The issue with this approach is it always returns nil from *AVAssetReaderVideoCompositionOutput.copyNextSampleBuffer()*.

----------
 5. Manually changing the timestamp of the frame with **CMSampleTimingInfo**, as suggested [here][8] Something like:

```
var sampleTimingInfo = CMSampleTimingInfo()
var sampleBufferToWrite: CMSampleBuffer?

CMSampleBufferGetSampleTimingInfo(vBuffer, at: 0, timingInfoOut: &amp;sampleTimingInfo)

sampleTimingInfo.duration = CMTimeMake(value: 100, timescale: Int32(videoConfig.videoFrameRate * 100))

sampleTimingInfo.presentationTimeStamp = CMTimeAdd(previousPresentationTimeStamp, sampleTimingInfo.duration)

previousPresentationTimeStamp = sampleTimingInfo.presentationTimeStamp

let status = CMSampleBufferCreateCopyWithNewTiming(allocator: kCFAllocatorDefault, sampleBuffer: vBuffer,sampleTimingEntryCount: 1, sampleTimingArray: &amp;sampleTimingInfo, sampleBufferOut: &amp;sampleBufferToWrite)
```
With this approach, I do get the frame rate set just right, but it increases the video duration (as mentioned in the comment of that question’s answer). I think at some point I may have to discard some frames (if the target frame rate is lower; I need to lower the frame rate in most of the cases). 

If I know that if I want 30fps, and my current frame rate is 60fps, it&#39;s simple to discard every second frame and setting the SampleBuffer time accordingly.

If I go with this approach(i.e. setting 23.98 fps), how do I decide which frame to discard and if the target frame rate is higher, which frame to duplicate? Reminder: the frame rate could be in fractions.

----------


  [1]: https://developer.apple.com/documentation/avfoundation/avassetwriterinputpixelbufferadaptor
  [2]: https://stackoverflow.com/a/16911799/1208191
  [3]: https://gist.github.com/chauhan130/31b8bf648f0071a949d1627c78315056#file-gistfile1-txt-L16
  [4]: https://gist.github.com/chauhan130/31b8bf648f0071a949d1627c78315056#file-gistfile1-txt-L38
  [5]: https://gist.github.com/chauhan130/31b8bf648f0071a949d1627c78315056#file-gistfile1-txt-L50
  [6]: https://github.com/rs/SDAVAssetExportSession
  [7]: https://gist.github.com/chauhan130/8d2f5bbe680353961fecacb80e254b92#file-gistfile1-txt-L77
  [8]: https://stackoverflow.com/a/49236475/1208191

Content Type	Original Author	Original Content on Stackoverflow
Question	Ravi Sharma	View Question on Stackoverflow
Solution 1 - Video	AlphaMale	View Answer on Stackoverflow
Solution 2 - Video	Jorgen	View Answer on Stackoverflow

What is the difference between H.264 video and MPEG-4 video?

Video Problem Overview

Video Solutions

Solution 1 - Video

Solution 2 - Video

Converting em to px in Javascript (and getting default font size)

Unable to run .net app with Mono - mscorlib.dll not found (version mismatch?)

Attributions