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()

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