diff options
| -rw-r--r-- | media/java/android/media/MediaCodec.java | 31 | ||||
| -rw-r--r-- | media/java/android/media/MediaRecorder.java | 7 |
2 files changed, 38 insertions, 0 deletions
diff --git a/media/java/android/media/MediaCodec.java b/media/java/android/media/MediaCodec.java index cc05ecd3f18e..8b9153621165 100644 --- a/media/java/android/media/MediaCodec.java +++ b/media/java/android/media/MediaCodec.java @@ -72,6 +72,37 @@ import java.util.concurrent.locks.ReentrantLock; Finally, you request (or receive) a filled output buffer, consume its contents and release it back to the codec. + <h3 id=qualityFloor><a name="qualityFloor">Minimum Quality Floor for Video Encoding</h3> + <p> + Beginning with {@link android.os.Build.VERSION_CODES#S}, Android's Video MediaCodecs enforce a + minimum quality floor. The intent is to eliminate poor quality video encodings. This quality + floor is applied when the codec is in Variable Bitrate (VBR) mode; it is not applied when + the codec is in Constant Bitrate (CBR) mode. The quality floor enforcement is also restricted + to a particular size range; this size range is currently for video resolutions + larger than 320x240 up through 1920x1080. + + <p> + When this quality floor is in effect, the codec and supporting framework code will work to + ensure that the generated video is of at least a "fair" or "good" quality. The metric + used to choose these targets is the VMAF (Video Multi-method Assessment Function) with a + target score of 70 for selected test sequences. + + <p> + The typical effect is that + some videos will generate a higher bitrate than originally configured. This will be most + notable for videos which were configured with very low bitrates; the codec will use a bitrate + that is determined to be more likely to generate an "fair" or "good" quality video. Another + situation is where a video includes very complicated content (lots of motion and detail); + in such configurations, the codec will use extra bitrate as needed to avoid losing all of + the content's finer detail. + + <p> + This quality floor will not impact content captured at high bitrates (a high bitrate should + already provide the codec with sufficient capacity to encode all of the detail). + The quality floor does not operate on CBR encodings. + The quality floor currently does not operate on resolutions of 320x240 or lower, nor on + videos with resolution above 1920x1080. + <h3>Data Types</h3> <p> Codecs operate on three kinds of data: compressed data, raw audio data and raw video data. diff --git a/media/java/android/media/MediaRecorder.java b/media/java/android/media/MediaRecorder.java index 341bb8d5309a..7d80e931c943 100644 --- a/media/java/android/media/MediaRecorder.java +++ b/media/java/android/media/MediaRecorder.java @@ -1096,6 +1096,13 @@ public class MediaRecorder implements AudioRouting, * clipped internally to ensure the video recording can proceed smoothly based on * the capabilities of the platform. * + * <p> + * NB: the actual bitrate and other encoding characteristics may be affected by + * the minimum quality floor behavior introduced in + * {@link android.os.Build.VERSION_CODES#S}. More detail on how and where this + * impacts video encoding can be found in the + * {@link MediaCodec} page and looking for "quality floor" (near the top of the page). + * * @param bitRate the video encoding bit rate in bits per second. */ public void setVideoEncodingBitRate(int bitRate) { |