public abstract class VideoReader

Object
VideoReader

Decodes an existing video clip into individual RGBA frames and PCM audio. This is the read side that com.codename1.media.Media deliberately does not provide: Media is a player whose Media#setTime(int) snaps to key frames and gives no exact frame guarantee, whereas VideoReader decodes to precise frames.

Two access patterns are offered:

#frameAt(long) returns the single frame at (or nearest before) a given millisecond offset. This is frame accurate, unlike seeking a Media player.
#readFrames(float, FrameCallback) walks the whole clip emitting frames at a fixed target frame rate. Source clips are frequently variable frame rate (VFR), for example screen recordings; this resamples them to a constant frame rate (CFR) so the caller receives an evenly spaced sequence it can re-encode or process.

The audio track, when present, is exposed as interleaved PCM through #readAudio().

Obtain an instance from VideoIO#openReader(String). Always #close() it when done.

Nested types

interface VideoReader.FrameCallback Callback used by VideoReader#readFrames(float, FrameCallback) to receive frames as they are decoded.

Constructors

public VideoReader()

Methods

`public abstract int getWidth()`	The width of the video track in pixels, or -1 if there is no video.
`public abstract int getHeight()`	The height of the video track in pixels, or -1 if there is no video.
`public abstract long getDurationMillis()`	The total duration of the clip in milliseconds, or -1 if unknown.
`public abstract float getFrameRate()`	The average/nominal frame rate of the source video track.
`public abstract boolean hasVideo()`	True if the clip has a decodable video track.
`public abstract boolean hasAudio()`	True if the clip has a decodable audio track.
`public abstract int getAudioSampleRate()`	The sample rate of the audio track in Hz, or -1 if there is no audio.
`public abstract int getAudioChannels()`	The number of channels in the audio track, or -1 if there is no audio.
`public abstract` `VideoFrame frameAt(long millis) throws IOException`	Returns the frame at (or nearest at/before) the given timestamp, decoded to RGBA.
`public abstract void readFrames(float fps,` `VideoReader.FrameCallback callback) throws IOException`	Walks the entire clip, decoding and resampling it to the requested constant frame rate, invoking the callback once per output frame in increasing timestamp order.
`public abstract` `AudioBuffer readAudio() throws IOException`	Reads the entire audio track and returns it as a single `AudioBuffer` of interleaved floating point samples.
`public abstract void close() throwsIOException`	Releases the decoder and any native resources.

Inherited methods

From Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait, clone

Constructor details

VideoReader

public VideoReader()

Method details

getWidth

public abstract int getWidth()

The width of the video track in pixels, or -1 if there is no video.

getHeight

public abstract int getHeight()

The height of the video track in pixels, or -1 if there is no video.

getDurationMillis

public abstract long getDurationMillis()

The total duration of the clip in milliseconds, or -1 if unknown.

getFrameRate

public abstract float getFrameRate()

The average/nominal frame rate of the source video track. For variable frame rate sources this is an average; use #readFrames(float, FrameCallback) to obtain an evenly spaced sequence.

hasVideo

public abstract boolean hasVideo()

True if the clip has a decodable video track.

hasAudio

public abstract boolean hasAudio()

True if the clip has a decodable audio track.

getAudioSampleRate

public abstract int getAudioSampleRate()

The sample rate of the audio track in Hz, or -1 if there is no audio.

getAudioChannels

public abstract int getAudioChannels()

The number of channels in the audio track, or -1 if there is no audio.

frameAt

public abstract VideoFrame frameAt(long millis)
throws IOException

Returns the frame at (or nearest at/before) the given timestamp, decoded to RGBA. Unlike seeking a Media player, the returned frame corresponds exactly to the requested position rather than the closest key frame.

Parameters

millis long: the timestamp to seek to in milliseconds

Returns

the decoded VideoFrame, or null if the position is past the end of the clip

Throws

IOException: if decoding fails

readFrames

public abstract void readFrames(float fps, VideoReader.FrameCallback callback)
throws IOException

Walks the entire clip, decoding and resampling it to the requested constant frame rate, invoking the callback once per output frame in increasing timestamp order. This converts a variable frame rate source to a constant frame rate sequence by duplicating or dropping source frames as needed.

Parameters

fps float: the target constant output frame rate in frames per second
callback VideoReader.FrameCallback: receives each decoded frame; return false from it to stop early

Throws

IOException: if decoding fails

readAudio

public abstract AudioBuffer readAudio()
throws IOException

Reads the entire audio track and returns it as a single AudioBuffer of interleaved floating point samples. For very long clips consider using the audio only at a reduced rate or processing the clip in segments, as the whole track is held in memory.

Returns

the decoded audio, or null if the clip has no audio track

Throws

IOException: if decoding fails

close

public abstract void close()
throws IOException

Releases the decoder and any native resources. The reader cannot be used after this call.

Throws

IOException: if releasing resources fails