From Multimedia File

Read multimedia file

Library

Sources

dspsrcs4

Description

The From Multimedia File block reads audio samples, video frames, or both from a multimedia file. The block imports data from the file into a Simulink® model.

    Note:   This block supports code generation for the host computer that has file I/O available. You cannot use this block with Real-Time Windows Target™ software because that product does not support file I/O.

The generated code for this block relies on prebuilt library files. You can run this code outside the MATLAB® environment, or redeploy it, but be sure to account for these extra library files when doing so. The packNGo function creates a single zip file containing all of the pieces required to run or rebuild this code. See packNGo for more information.

To run an executable file that was generated from a model containing this block, you may need to add precompiled shared library files to your system path. See Understanding C Code Generation for details.

Supported Platforms and File Types

The supported file formats available to you depends on the codecs installed on your system.

Windows Platforms Supported File Formats

With the necessary Windows® DirectShow codecs installed on your system, the From Multimedia File Block supports many video and audio file formats. This block performs best on platforms with Version 9.0 or later of DirectX® software.

The following table lists the most common file formats.

Multimedia TypesFile Name Extensions
Image files.jpg,.bmp,.png
Video files.qt, .mov, .avi, .asf, .asx, .wmv, .mpg, .mpeg, .mp2, .mp4, .m4v
Audio files.wav, .wma, .aif, .aifc, .aiff, .mp3, .au, .snd, .mp4, .m4a, .flac, .ogg

The default for image files is .png, , for video files is .avi, and for audio files is .mp3.

Windows XP x64 platform ships with a limited set of 64-bit video and audio codecs. If the From Multimedia File block cannot work on a compressed multimedia file, try one of the two alternatives:

  • Run the 32-bit version of MATLAB on your Windows XP x64 platform. Windows XP x64 ships with many 32-bit codecs.

  • Save the multimedia file to a file format supported by the From Multimedia File block.

If you use Windows, use Windows Media® Player Version 11 or later with this block for best results.

Non-Windows Platform Supported File Formats

The following table lists the most common file formats.


Multimedia TypesFile Name Extensions
Video files.avi, .mj2, .mov, .mp4,.m4v
Audio filesUncompressed .avi, .mp3, .mp4, .m4a, .wav, .flac, .ogg

The default for video files is .avi, and for audio files is .mp3.

Ports

The output ports of the From Multimedia File block change according to the content of the multimedia file. If the file contains only video frames, the Image, intensity I, or R,G,B ports appear on the block. If the file contains only audio samples, the Audio port appears on the block. If the file contains both audio and video, you can select the data to emit. The following table describes available ports.

PortDescription
Image

M-by-N-by-P color video signal where P is the number of color planes.

I

M-by-N matrix of intensity values.

R, G, B

Matrix that represents one plane of the RGB video stream. Outputs from the R, G, or B ports must have same dimensions.

Audio

Vector of audio data.

Y, Cb, Cr

Matrix that represents one frame of the YCbCr video stream. The Y, Cb, Cr ports produce the following outputs:

Y: M x N
Cb: M xN2
Cr: M xN2

Sample Rates

The sample rate that the block uses depends on the audio and video sample rate. While the FMMF block operates at a single rate in Simulink, the underlying audio and video streams can produce different rates. In some cases, when the block outputs both audio and video, makes a small adjustment to the video rate.

Sample Time Calculations Used for Video and Audio Files

Sample time = ceil(AudioSampleRateFPS)AudioSampleRate.
When audio sample time, AudioSampleRateFPS is noninteger, the equation cannot reduce to 1FPS.

In this case, to prevent synchronization problems, the block drops the corresponding video frame when the audio stream leads the video stream by more than 1FPS.
In summary, the block outputs one video frame at each Simulink time step. To calculate the number of audio samples to output at each time step, the block divides the audio sample rate by the video frame rate (fps). If the audio sample rate does not divide evenly by the number of video frames per second, the block rounds the number of audio samples up to the nearest whole number. If necessary, the block periodically drops a video frame to maintain synchronization for large files.

Dialog Box

The Main pane of the From Multimedia File block dialog appears as follows.

File name

Specify the name of the multimedia file from which to read. The block determines the type of file (audio and video, audio only, or video only) and provides the associated parameters.

If the location of the file does not appear on your MATLAB path, use the Browse button to specify the full path. Otherwise, if the location of this file appears on your MATLAB path, enter only the file name. On Windows platforms, this parameter supports URLs that point to MMS (Microsoft Media Server) streams.

Inherit sample time from file

Select the Inherit sample time from file check box if you want the block sample time to be the same as the multimedia file. If you clear this check box, enter the block sample time in the Desired sample time parameter field. The file that the From Multimedia File block references, determines the block default sample time. You can also set the sample time for this block manually. If you do not know the intended sample rate of the video, let the block inherit the sample rate from the multimedia file.

Desired sample time

Specify the block sample time. This parameter becomes available if you clear the Inherit sample time from file check box.

Number of times to play file

Enter a positive integer or inf to represent the number of times to play the file.

Output end-of-file indicator

Use this check box to determine whether the output is the last video frame or audio sample in the multimedia file. When you select this check box, a Boolean output port labeled EOF appears on the block. The output from the EOF port defaults to 1 when the last video frame or audio sample is output from the block. Otherwise, the output from the EOF port defaults to 0.

Multimedia outputs

Specify Video and audio, Video only, or Audio only output file type. This parameter becomes available only when a video signal has both audio and video.

Samples per audio channel

Specify number of samples per audio channel. This parameter becomes available for files containing audio.

Output color format

Specify whether you want the block to output RGB, Intensity, or YCbCr 4:2:2 video frames. This parameter becomes available only for a signal that contains video. If you select RGB, use the Image signal parameter to specify how to output a color signal.

Image signal

Specify how to output a color video signal. If you select One multidimensional signal, the block outputs an M-by-N-by-P color video signal, where P is the number of color planes, at one port. If you select Separate color signals, additional ports appear on the block. Each port outputs one M-by-N plane of an RGB video stream. This parameter becomes available only if you set the Image color space parameter to RGB and the signal contains video.

Audio output sampling mode

Select Sample based or Frame based output. If the input to the block has 3 or more dimensions, you must select Sample based output. This parameter appears when you specify a file containing audio for the File name parameter.

The Data Types pane of the To Multimedia File block dialog box appears as follows.

Audio output data type

Set the data type of the audio samples output at the Audio port. This parameter becomes available only if the multimedia file contains audio. You can choose double, single, int16, or uint8 types.

Video output data type

Set the data type of the video frames output at the R, G, B, or Image ports. This parameter becomes available only if the multimedia file contains video. You can choose double, single, int8, uint8, int16, uint16, int32, uint32, or Inherit from file types.

Troubleshooting

Running an Executable Outside MATLAB

To run your generated standalone executable application in Shell, you need to set your environment to the following:

PlatformCommand
Macsetenv DYLD_LIBRARY_PATH $LD_LIBRARY_PATH: $MATLABROOT/bin/maci64 (csh/tcsh)

export DYLD_LIBRARY_PATH $LD_LIBRARY_PATH: $MATLABROOT/bin/maci64 (Bash)

Linuxsetenv LD_LIBRARY_PATH $LD_LIBRARY_PATH: $MATLABROOT/bin/glnxa64 (csh/tcsh)

export LD_LIBRARY_PATH $LD_LIBRARY_PATH: $MATLABROOT/bin/glnxa64 (Bash)

Windowsset PATH = $MATLABROOT\bin\win32;%PATH%

set PATH = $MATLABROOT\bin\win64;%PATH%

Supported Data Types

For source blocks to display video data properly, double- and single-precision floating-point pixel values must be between 0 and 1. For other data types, the pixel values must be between the minimum and maximum values supported by their data type.

PortSupported Data TypesSupports Complex Values?

Image

  • Double-precision floating point

  • Single-precision floating point

  • 8-, 16-, and 32-bit signed integers

  • 8-, 16-, and 32-bit unsigned integers

No

R, G, B

Same as the Image port

No

Audio

  • Double-precision floating point

  • Single-precision floating point

  • 16-bit signed integers

  • 8-bit unsigned integers

No

Y, Cb,Cr

Same as the Image port

No

See Also

To Multimedia FileDSP System Toolbox
Sample TimeSimulink

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