Android音视频开发 - MediaMetadataRetriever 相关
MediaMetadataRetriever 是android中用于从媒体文件中提取元数据新的类. 可以获取音频,视频和图像文件的各种信息,如时长,标题,封面等.
1:初始化对象
private MediaMetadataRetriever mediaMetadataRetriever = new MediaMetadataRetriever();
mediaMetadataRetriever.setDataSource(“sdcard/share.mp4”);
需要申请读写权限.
这里我使用的是本地路径, 需要注意的是如果路径文件不存在,会抛出
IllegalArgumentException,具体的源码如下:
public void setDataSource(String path) throws IllegalArgumentException {
if (path == null) {
throw new IllegalArgumentException();
}
try (FileInputStream is = new FileInputStream(path)) {
FileDescriptor fd = is.getFD();
setDataSource(fd, 0, 0x7ffffffffffffffL);
} catch (FileNotFoundException fileEx) {
throw new IllegalArgumentException();
} catch (IOException ioEx) {
throw new IllegalArgumentException();
}
}
2: extractMetadata
根据keyCode返回keyCode关联的元数据.
系统的keyCode如下:
/**
* The metadata key to retrieve the numeric string describing the
* order of the audio data source on its original recording.
*/
public static final int METADATA_KEY_CD_TRACK_NUMBER = 0;
/**
* The metadata key to retrieve the information about the album title
* of the data source.
*/
public static final int METADATA_KEY_ALBUM = 1;
/**
* The metadata key to retrieve the information about the artist of
* the data source.
*/
public static final int METADATA_KEY_ARTIST = 2;
/**
* The metadata key to retrieve the information about the author of
* the data source.
*/
public static final int METADATA_KEY_AUTHOR = 3;
/**
* The metadata key to retrieve the information about the composer of
* the data source.
*/
public static final int METADATA_KEY_COMPOSER = 4;
/**
* The metadata key to retrieve the date when the data source was created
* or modified.
*/
public static final int METADATA_KEY_DATE = 5;
/**
* The metadata key to retrieve the content type or genre of the data
* source.
*/
public static final int METADATA_KEY_GENRE = 6;
/**
* The metadata key to retrieve the data source title.
*/
public static final int METADATA_KEY_TITLE = 7;
/**
* The metadata key to retrieve the year when the data source was created
* or modified.
*/
public static final int METADATA_KEY_YEAR = 8;
/**
* The metadata key to retrieve the playback duration of the data source.
*/
public static final int METADATA_KEY_DURATION = 9;
/**
* The metadata key to retrieve the number of tracks, such as audio, video,
* text, in the data source, such as a mp4 or 3gpp file.
*/
public static final int METADATA_KEY_NUM_TRACKS = 10;
/**
* The metadata key to retrieve the information of the writer (such as
* lyricist) of the data source.
*/
public static final int METADATA_KEY_WRITER = 11;
/**
* The metadata key to retrieve the mime type of the data source. Some
* example mime types include: "video/mp4", "audio/mp4", "audio/amr-wb",
* etc.
*/
public static final int METADATA_KEY_MIMETYPE = 12;
/**
* The metadata key to retrieve the information about the performers or
* artist associated with the data source.
*/
public static final int METADATA_KEY_ALBUMARTIST = 13;
/**
* The metadata key to retrieve the numberic string that describes which
* part of a set the audio data source comes from.
*/
public static final int METADATA_KEY_DISC_NUMBER = 14;
/**
* The metadata key to retrieve the music album compilation status.
*/
public static final int METADATA_KEY_COMPILATION = 15;
/**
* If this key exists the media contains audio content.
*/
public static final int METADATA_KEY_HAS_AUDIO = 16;
/**
* If this key exists the media contains video content.
*/
public static final int METADATA_KEY_HAS_VIDEO = 17;
/**
* If the media contains video, this key retrieves its width.
*/
public static final int METADATA_KEY_VIDEO_WIDTH = 18;
/**
* If the media contains video, this key retrieves its height.
*/
public static final int METADATA_KEY_VIDEO_HEIGHT = 19;
/**
* This key retrieves the average bitrate (in bits/sec), if available.
*/
public static final int METADATA_KEY_BITRATE = 20;
/**
* This key retrieves the language code of text tracks, if available.
* If multiple text tracks present, the return value will look like:
* "eng:chi"
* @hide
*/
public static final int METADATA_KEY_TIMED_TEXT_LANGUAGES = 21;
/**
* If this key exists the media is drm-protected.
* @hide
*/
public static final int METADATA_KEY_IS_DRM = 22;
/**
* This key retrieves the location information, if available.
* The location should be specified according to ISO-6709 standard, under
* a mp4/3gp box "@xyz". Location with longitude of -90 degrees and latitude
* of 180 degrees will be retrieved as "-90.0000+180.0000", for instance.
*/
public static final int METADATA_KEY_LOCATION = 23;
/**
* This key retrieves the video rotation angle in degrees, if available.
* The video rotation angle may be 0, 90, 180, or 270 degrees.
*/
public static final int METADATA_KEY_VIDEO_ROTATION = 24;
/**
* This key retrieves the original capture framerate, if it's
* available. The capture framerate will be a floating point
* number.
*/
public static final int METADATA_KEY_CAPTURE_FRAMERATE = 25;
/**
* If this key exists the media contains still image content.
*/
public static final int METADATA_KEY_HAS_IMAGE = 26;
/**
* If the media contains still images, this key retrieves the number
* of still images.
*/
public static final int METADATA_KEY_IMAGE_COUNT = 27;
/**
* If the media contains still images, this key retrieves the image
* index of the primary image.
*/
public static final int METADATA_KEY_IMAGE_PRIMARY = 28;
/**
* If the media contains still images, this key retrieves the width
* of the primary image.
*/
public static final int METADATA_KEY_IMAGE_WIDTH = 29;
/**
* If the media contains still images, this key retrieves the height
* of the primary image.
*/
public static final int METADATA_KEY_IMAGE_HEIGHT = 30;
/**
* If the media contains still images, this key retrieves the rotation
* angle (in degrees clockwise) of the primary image. The image rotation
* angle must be one of 0, 90, 180, or 270 degrees.
*/
public static final int METADATA_KEY_IMAGE_ROTATION = 31;
/**
* If the media contains video and this key exists, it retrieves the
* total number of frames in the video sequence.
*/
public static final int METADATA_KEY_VIDEO_FRAME_COUNT = 32;
/**
* @hide
*/
public static final int METADATA_KEY_EXIF_OFFSET = 33;
/**
* @hide
*/
public static final int METADATA_KEY_EXIF_LENGTH = 34;
// Add more here...
如获取视频时长:
String METADATA_KEY_DURATION = mediaMetadataRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
Log.i(TAG, “onCreate: METADATA_KEY_DURATION=”+METADATA_KEY_DURATION);
3: getFrameAtTime
该方法在任何时间位置找到一个有代表性的帧，并将其作为位图返回.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
Bitmap frameAtTime = mediaMetadataRetriever.getFrameAtTime();
}
如果需要获取指定时间,则可以调用
public Bitmap getFrameAtTime(long timeUs) {
return getFrameAtTime(timeUs, OPTION_CLOSEST_SYNC);
}
4: getFrameAtIndex
用于从媒体文件中获取指定索引位置的帧图像.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
Bitmap frameAtIndex = mediaMetadataRetriever.getFrameAtIndex(0);
}
5: getImageAtIndex
基于0的图像索引,返回位图信息.
Bitmap imageAtIndex = mediaMetadataRetriever.getImageAtIndex(0);
这里调用该方法时,会抛出IllegalStateException :
java.lang.IllegalStateException: Does not contail still images
at android.media.MediaMetadataRetriever.getImageAtIndexInternal(MediaMetadataRetriever.java:648)
at android.media.MediaMetadataRetriever.getImageAtIndex(MediaMetadataRetriever.java:605)
at com.test.media.MainActivity.lambda$onCreate$0$MainActivity(MainActivity.java:50)
at com.test.media.-$$Lambda$MainActivity$fGcBDHveSBN77vUeMp6H1nheePE.onClick(Unknown Source:2)
at android.view.View.performClick(View.java:7259)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:967)
at android.view.View.performClickInternal(View.java:7236)
at android.view.View.access$3600(View.java:801)
at android.view.View$PerformClick.run(View.java:27892)
at android.os.Handler.handleCallback(Handler.java:894)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:491)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:940)
具体的错误信息的原因如下:
private Bitmap getImageAtIndexInternal(int imageIndex, @Nullable BitmapParams params) {
if (!“yes”.equals(extractMetadata(MediaMetadataRetriever.METADATA_KEY_HAS_IMAGE))) {
throw new IllegalStateException(“Does not contail still images”);
}
String imageCount = extractMetadata(MediaMetadataRetriever.METADATA_KEY_IMAGE_COUNT);
if (imageIndex >= Integer.parseInt(imageCount)) {
throw new IllegalArgumentException("Invalid image index: " + imageCount);
}
return _getImageAtIndex(imageIndex, params);
}
可以看到系统源码中校验了extractMetadata(MediaMetadataRetriever.METADATA_KEY_HAS_IMAGE)的值,如果值不是"yes",就会抛出"Does not contail still images".
与getImageAtIndex类似的方法还有:
getImageAtIndex(int, BitmapParams)
getPrimaryImage(BitmapParams)
getPrimaryImage()