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Title: Android hardware encoding and decoding [Print This Page]
Author: Andy    Time: 12/12/2014 11:41
Title: Android hardware encoding and decoding

Android hardware encoding mainly realized by MediaCodec.

The official documentation of Android shows as below.

  1. MediaCodec codec = MediaCodec.createDecoderByType(type);
  2. codec.configure(format, ...);
  3. codec.start();
  4. ByteBuffer[] inputBuffers = codec.getInputBuffers();
  5. ByteBuffer[] outputBuffers = codec.getOutputBuffers();
  6. for (;;) {
  7.    int inputBufferIndex = codec.dequeueInputBuffer(timeoutUs);
  8.    if (inputBufferIndex >= 0) {
  9.      // fill inputBuffers[inputBufferIndex] with valid data
  10.      ...
  11.      codec.queueInputBuffer(inputBufferIndex, ...);
  12.    }

  14.    int outputBufferIndex = codec.dequeueOutputBuffer(timeoutUs);
  15.    if (outputBufferIndex >= 0) {
  16.      // outputBuffer is ready to be processed or rendered.
  17.      ...
  18.      codec.releaseOutputBuffer(outputBufferIndex, ...);
  19.    } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
  20.      outputBuffers = codec.getOutputBuffers();
  21.    } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
  22.      // Subsequent data will conform to new format.
  23.      MediaFormat format = codec.getOutputFormat();
  24.      ...
  25.    }
  26. }
  27. codec.stop();
  28. codec.release();
  29. codec = null;
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We made a demo using MdeiaCodec to realize the hardware encoding and decoding of camera.

This is the GUI of the demo.


The GUI is simple，the preview of camera located at the lower right corner.

The window on the middle is the picture after decoding.

  1. private void doCodec(byte[] data){
  2.                 int et = mEncoder.encode(data , 0 , data.length, buffer1, 0);
  3.                 Log.d("buncodec","encode et="+et);
  4.                  
  5.                 int dt = mDecoder.decode(buffer1, 0 , et , buffer2 , 0);
  6.                 Log.d("buncodec","decode dt="+dt);
  7.                  
  8.                  
  9.                 // The data of NV21 showed by YUV Image, efficient less, just a demo.
  10.         YuvImage image = new YuvImage(buffer2,
  11.                 getPreviewFormat(), getPreviewWidth(), getPreviewHeight(),
  12.                 null);
  13.         setData(image,getPreviewWidth(),getPreviewHeight());
  14.          
  15.         image = null ;
  16.         }
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The information of logcat show as below:


From the information above, you can see the preview data length of 1280*720 pixels is 1280*720*3/2=1382400；

Et stands for the length after encoding,it’s within 50000.

Dt stands for the length after decoding,it’s back to 1382400.

Author: ZZP    Time: 12/13/2014 09:26
handsome boy



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