Audio and Video Muxing

You can call the native APIs provided by the AVMuxer module to mux audio and video streams, that is, to store encoded audio and video data to a file in a certain format.

Currently, the following muxer capabilities are supported:

Usage Scenario

• Video and audio recording

  After you encode audio and video streams, mux them into files.

• Audio and video editing

  After you edit audio and video, mux them into files.

• Audio and video transcoding

  After you transcode audio and video, mux them into files.

How to Develop

Read AVMuxer for the API reference.

NOTE

To call the muxer APIs to write a local file, request the ohos.permission.READ_MEDIA and ohos.permission.WRITE_MEDIA permissions by following the instructions provided in Requesting User Authorization.

Linking the Dynamic Library in the CMake Script

target_link_libraries(sample PUBLIC libnative_media_avmuxer.so)
target_link_libraries(sample PUBLIC libnative_media_core.so)

How to Develop

The following walks you through how to implement the entire process of audio and video muxing. It uses the MP4 format as an example.

1. Add the header files.

   #include <multimedia/player_framework/native_avmuxer.h>
   #include <multimedia/player_framework/native_avcodec_base.h>
   #include <multimedia/player_framework/native_avformat.h>
   #include <multimedia/player_framework/native_avbuffer.h>
   

2. Call OH_AVMuxer_Create() to create an OH_AVMuxer instance.

   // Set the muxing format to MP4.
   OH_AVOutputFormat format = AV_OUTPUT_FORMAT_MPEG_4;
   // Create a File Descriptor (FD) in read/write mode.
   int32_t fd = open("test.mp4", O_CREAT | O_RDWR | O_TRUNC, S_IRUSR | S_IWUSR);
   OH_AVMuxer *muxer = OH_AVMuxer_Create(fd, format);
   

3. (Optional) Call OH_AVMuxer_SetRotation() to set the rotation angle.

   // Set the rotation angle when a video image needs to be rotated.
   OH_AVMuxer_SetRotation(muxer, 0);
   

4. Add an audio track.

   Method 1: Use OH_AVFormat_Create to create the format.

   int audioTrackId = -1;
   uint8_t *buffer = ...; // Encoding configuration data. If there is no configuration data, leave the parameter unspecified.
   size_t size =...; // Length of the encoding configuration data. Set this parameter based on project requirements.
   OH_AVFormat *formatAudio = OH_AVFormat_Create();
   OH_AVFormat_SetStringValue(formatAudio, OH_MD_KEY_CODEC_MIME, OH_AVCODEC_MIMETYPE_AUDIO_AAC); // Mandatory.
   OH_AVFormat_SetIntValue(formatAudio, OH_MD_KEY_AUD_SAMPLE_RATE, 44100); // Mandatory.
   OH_AVFormat_SetIntValue(formatAudio, OH_MD_KEY_AUD_CHANNEL_COUNT, 2); // Mandatory.
   OH_AVFormat_SetIntValue(formatAudio, OH_MD_KEY_PROFILE, AAC_PROFILE_LC); // Optional.
   OH_AVFormat_SetBuffer(formatAudio, OH_MD_KEY_CODEC_CONFIG, buffer, size); // Optional.
   
   int ret = OH_AVMuxer_AddTrack(muxer, &audioTrackId, formatAudio);
   if (ret != AV_ERR_OK || audioTrackId < 0) {
       // Failure to add the audio track.
   }
   OH_AVFormat_Destroy (formatAudio); // Destroy the format.
   

   Method 2: Use OH_AVFormat_CreateAudioFormat to create the format.

   int audioTrackId = -1;
   uint8_t *buffer = ...; // Encoding configuration data. If there is no configuration data, leave the parameter unspecified.
   size_t size =...; // Length of the encoding configuration data. Set this parameter based on project requirements.
   OH_AVFormat *formatAudio = OH_AVFormat_CreateAudioFormat(OH_AVCODEC_MIMETYPE_AUDIO_AAC, 44100, 2);
   OH_AVFormat_SetIntValue(formatAudio, OH_MD_KEY_PROFILE, AAC_PROFILE_LC); // Optional.
   OH_AVFormat_SetBuffer(formatAudio, OH_MD_KEY_CODEC_CONFIG, buffer, size); // Optional.
   
   int ret = OH_AVMuxer_AddTrack(muxer, &audioTrackId, formatAudio);
   if (ret != AV_ERR_OK || audioTrackId < 0) {
       // Failure to add the audio track.
   }
   OH_AVFormat_Destroy (formatAudio); // Destroy the format.
   

5. Add a video track.

   Method 1: Use OH_AVFormat_Create to create the format.

   int videoTrackId = -1;
   uint8_t *buffer = ...; // Encoding configuration data. If there is no configuration data, leave the parameter unspecified.
   size_t size =...; // Length of the encoding configuration data. Set this parameter based on project requirements.
   OH_AVFormat *formatVideo = OH_AVFormat_Create();
   OH_AVFormat_SetStringValue(formatVideo, OH_MD_KEY_CODEC_MIME, OH_AVCODEC_MIMETYPE_VIDEO_AVC); // Mandatory.
   OH_AVFormat_SetIntValue(formatVideo, OH_MD_KEY_WIDTH, 1280); // Mandatory.
   OH_AVFormat_SetIntValue(formatVideo, OH_MD_KEY_HEIGHT, 720); // Mandatory.
   OH_AVFormat_SetBuffer(formatVideo, OH_MD_KEY_CODEC_CONFIG, buffer, size); // Optional
   
   int ret = OH_AVMuxer_AddTrack(muxer, &videoTrackId, formatVideo);
   if (ret != AV_ERR_OK || videoTrackId < 0) {
       // Failure to add the video track.
   }
   OH_AVFormat_Destroy(formatVideo); // Destroy the format.
   

   Method 2: Use OH_AVFormat_CreateVideoFormat to create the format.

   int videoTrackId = -1;
   uint8_t *buffer = ...; // Encoding configuration data. If there is no configuration data, leave the parameter unspecified.
   size_t size =...; // Length of the encoding configuration data. Set this parameter based on project requirements.
   OH_AVFormat *formatVideo = OH_AVFormat_CreateVideoFormat(OH_AVCODEC_MIMETYPE_VIDEO_AVC, 1280, 720);
   OH_AVFormat_SetBuffer(formatVideo, OH_MD_KEY_CODEC_CONFIG, buffer, size); // Optional
   
   int ret = OH_AVMuxer_AddTrack(muxer, &videoTrackId, formatVideo);
   if (ret != AV_ERR_OK || videoTrackId < 0) {
       // Failure to add the video track.
   }
   OH_AVFormat_Destroy(formatVideo); // Destroy the format.
   

6. Add a cover track.

   Method 1: Use OH_AVFormat_Create to create the format.

   int coverTrackId = -1;
   OH_AVFormat *formatCover = OH_AVFormat_Create();
   OH_AVFormat_SetStringValue(formatCover, OH_MD_KEY_CODEC_MIME, OH_AVCODEC_MIMETYPE_IMAGE_JPG);
   OH_AVFormat_SetIntValue(formatCover, OH_MD_KEY_WIDTH, 1280);
   OH_AVFormat_SetIntValue(formatCover, OH_MD_KEY_HEIGHT, 720);
   
   int ret = OH_AVMuxer_AddTrack(muxer, &coverTrackId, formatCover);
   if (ret != AV_ERR_OK || coverTrackId < 0) {
       // Failure to add the cover track.
   }
   OH_AVFormat_Destroy(formatCover); // Destroy the format.
   

   Method 2: Use OH_AVFormat_CreateVideoFormat to create the format.

   int coverTrackId = -1;
   OH_AVFormat *formatCover = OH_AVFormat_CreateVideoFormat(OH_AVCODEC_MIMETYPE_IMAGE_JPG, 1280, 720);
   
   int ret = OH_AVMuxer_AddTrack(muxer, &coverTrackId, formatCover);
   if (ret != AV_ERR_OK || coverTrackId < 0) {
       // Failure to add the cover track.
   }
   OH_AVFormat_Destroy(formatCover); // Destroy the format.
   

7. Call OH_AVMuxer_Start() to start muxing.

   // Call Start() to write the file header. After this API is called, you cannot set media parameters or add tracks.
   if (OH_AVMuxer_Start(muxer) != AV_ERR_OK) {
       // Exception handling.
   }
   

8. Call OH_AVMuxer_WriteSampleBuffer() to write data.

   including video, audio, and cover data.

   // Data can be written only after Start() is called.
   int size = ...;
   OH_AVBuffer *sample = OH_AVBuffer_Create (size); // Create an AVBuffer instance.
   // Write data to the sample buffer by using OH_AVBuffer_GetAddr(sample). For details, see the usage of OH_AVBuffer.
   // Mux the cover. One image must be written at a time.
   
   // Set buffer information.
   OH_AVCodecBufferAttr info;
   info.pts =...; // Playback start time of the current data, in microseconds. The relative time is used.
   info.size = size; // Length of the current data.
   info.offset = 0; // Offset. Generally, the value is 0.
   info.flags |= AVCODEC_BUFFER_FLAGS_SYNC_FRAME; // Flag of the current data. For details, see OH_AVCodecBufferFlags.
   info.flags |= AVCODEC_BUFFER_FLAGS_CODEC_DATA; // The AVC in annex-b format contains the codec configuration flag.
   OH_AVBuffer_SetBufferAttr(sample, &info); // Set the buffer attribute.
   int trackId = audioTrackId; // Select the track to be written.
   
   int ret = OH_AVMuxer_WriteSampleBuffer(muxer, trackId, sample);
   if (ret != AV_ERR_OK) {
       // Exception handling.
   }
   

9. Call OH_AVMuxer_Stop() to stop muxing.

   // Call Stop() to write the file trailer. After this API is called, you cannot write media data.
   if (OH_AVMuxer_Stop(muxer) != AV_ERR_OK) {
       // Exception handling.
   }
   

10. Call OH_AVMuxer_Destroy() to release the instance.

    if (OH_AVMuxer_Destroy(muxer) != AV_ERR_OK) {
        // Exception handling.
    }
    muxer = NULL;
    close(fd); // Close the FD.