Media Codec: Encoding and Decoding Media Files

This tutorial demonstrates how you can encode and decode media files.

Warm-up

Become familiar with the Media Codec API basics by learning about:

• Initializing Media Codecs

  Initialize the media codecs for use.

• Managing Media Codecs

  Prepare and start the codec.

• Releasing Resources

  Reset the codec and destroy the handle.

Initializing Media Codecs

Before using the Media codec:

1. To use the functions and data types of the Media Codec API (in mobile and wearable applications), include the <media_codec.h> header file in your application:

   #include <media_codec.h>
   

2. Define a handle for the media codec and pass it to the mediacodec_create() function. The handle must be passed to all other Media Codec APIs.

   mediacodec_h *mediacodec;
   ret = mediacodec_create(&mediacodec);

3. If the handle is created normally, set the codec and configuration using the mediacodec_set_codec() function.

   The enumerations mediacodec_codec_type_e (in mobile and wearable applications) and mediacodec_support_type_e (in mobile and wearable applications) define the media codec type and support type.

   ret = mediacodec_set_codec(mediacodec, (mediacodec_codec_type_e)codecid, flag); 

4. Set the video decoder using the mediacodec_set_vdec_info() or mediacodec_set_venc_info() function.

   ret = mediacodec_set_vdec_info(mediacodec, width, height);
   
   // Or
   
   ret = mediacodec_set_venc_info(mediacodec, width, height, fps, target_bits);

Managing Media Codecs

The Media Codec usage follows a basic pattern:

1. Create and configure the Media Codec handle.
2. Loop until done:
   • If an input buffer is ready, read a chunk of input and copy it into the buffer.
   • If an output buffer is ready, copy the output from the buffer.
3. Release the Media Codec handle.

To manage the codec process loop:

1. If the prerequisites are set normally, prepare the media codec using the mediacodec_prepare() function.

   ret = mediacodec_prepare(mediacodec);
   

2. Start the media codec using the mediacodec_process_input() and mediacodec_get_output() functions.

   media_packet_h in_buf = NULL;
   ret = mediacodec_process_input (mediacodec, in_buf, 0);
   
   media_packet_h output_buf = NULL;
   ret = mediacodec_get_output (mediacodec, &output_buf, 0);
   

Releasing Resources

To reset the codec and destroy the handle using the mediacodec_unprepare() and mediacodec_destroy() functions after you have finished work with the media codec:

ret = mediacodec_unprepare(mediacodec);

ret = mediacodec_destroy(mediacodec);

Afterwards, the media codec state is changed to MEDIACODEC_STATE_NONE.