My goal is to write out a video file with custom-drawn content in each frame, using CGContext. I'm having an issue where after I hit input.markCurrentPassAsFinished(), I get a crash, because [AVAssetWriterInputMediaDataRequester delegate]: message sent to deallocated instance 0x60c00025fa40
But AVAssetWriterInputMediaDataRequester is not a documented class, so I don't know what object isn't being kept around long enough.
Code:
import Foundation
import AVFoundation
import CoreMedia
import Cocoa
class VideoRenderer {
//my demo data model
let title:String
let outputUrl:URL
var progress:Progress
let writer : AVAssetWriter
let completion:(Bool)->()
init(title:String, outputUrl:URL, completion:@escaping(Bool)->()) throws {
self.title = title
self.outputUrl = outputUrl
self.completion = completion
progress = Progress(parent: nil, userInfo: nil)
writer = try AVAssetWriter(outputURL: outputUrl, fileType: .mp4)
/* guard let pixelPool = CVPixelBufferPool.create(width: 1280, height: 720)
else {
throw PoolCreatorError.cantEven
}
self.pixelPool = pixelPool */
}
func export() {
//must specify AVVideoCodecKey, AVVideoWidthKey, and AVVideoHeightKey
//AVVideoCodecKey = AVVideoCodecTypeH264
let input = AVAssetWriterInput(mediaType: .video, outputSettings: [
AVVideoCodecKey : AVVideoCodecType.h264,
AVVideoWidthKey:1280,
AVVideoHeightKey:720,
AVVideoCompressionPropertiesKey:[
AVVideoAverageBitRateKey:2600000 as NSNumber
,AVVideoExpectedSourceFrameRateKey:30.0 as NSNumber
// ,AVVideoAverageNonDroppableFrameRateKey:30 as NSNumber //not supported for H.264
]
//lots of additional keys related to colors
])
input.mediaTimeScale = 30000 //to support 29.97 for NTSC
writer.add(input)
inputWriter = input
let bufferAdapter = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: input, sourcePixelBufferAttributes: [
kCVPixelBufferCGBitmapContextCompatibilityKey as String:true,
kCVPixelBufferWidthKey as String:1280 as CFNumber,
kCVPixelBufferHeightKey as String:720 as CFNumber,
kCVPixelBufferPixelFormatTypeKey as String:kCVPixelFormatType_32ARGB
] )
pixelBufferAdapter = bufferAdapter
if !writer.startWriting() {
completion(false)
return
}
writer.startSession(atSourceTime:CMTime(seconds: 0.0, preferredTimescale: 30) /*CMTime(value: 0, timescale: 30)*/)
input.respondToEachPassDescription(on: DispatchQueue.global(qos: .userInitiated)) {
guard let timeRange:CMTimeRange = input.currentPassDescription?.sourceTimeRanges.first?.timeRangeValue else {
//we're done
self.writer.finishWriting(completionHandler: {
self.didComplete()
//self.pixelBufferAdapter = nil
})
return
}
self.lastGeneratedTime = timeRange.start.seconds
input.requestMediaDataWhenReady(on: DispatchQueue.global(qos: .userInitiated)) {
while input.isReadyForMoreMediaData {
//get time
let thisTimeStamp = CMTime(seconds: self.lastGeneratedTime, preferredTimescale: input.mediaTimeScale)
if thisTimeStamp.seconds >= 2.0 { //compare to end of timeRange
input.markCurrentPassAsFinished()
return
}
let nextTime:Double = self.lastGeneratedTime + (1/30.0)
//print("thisTime = \(thisTimeStamp.seconds)")
//if over, cancel render
guard let buffer:CVPixelBuffer = bufferAdapter.pixelBufferDrawing({ context in
//TODO: draw frame
context.setFillColor(NSColor.blue.cgColor)
context.fill(CGRect(x: 0.0, y: 0.0, width: 1280.0, height: 720.0))
}) else {
continue
}
if !bufferAdapter.append(buffer, withPresentationTime: thisTimeStamp) {
print("didn't append")
}
self.lastGeneratedTime = nextTime
}
}
}
//endsession?
}
//var pixelPool:CVPixelBufferPool
func didComplete() {
if writer.status != .completed
,let error = writer.error {
print("writer error = \(error)")
}
completion(writer.status == .completed)
}
var lastGeneratedTime:Double = 0.0
var pixelBufferAdapter:AVAssetWriterInputPixelBufferAdaptor?
var inputWriter:AVAssetWriterInput?
}
extension AVAssetWriterInputPixelBufferAdaptor {
func pixelBufferDrawing(_ work:(CGContext)->())->CVPixelBuffer? {
var bufferOrNil:CVPixelBuffer?
guard let pool = pixelBufferPool
,CVPixelBufferPoolCreatePixelBuffer(nil, pool, &bufferOrNil) == kCVReturnSuccess
,let buffer = bufferOrNil
else {
return nil
}
let width:Int = CVPixelBufferGetWidth(buffer)
let height:Int = CVPixelBufferGetHeight(buffer)
CVPixelBufferLockBaseAddress(buffer, [])
//create a cg graphics context using the pixel buffer's data bytes
let data = CVPixelBufferGetBaseAddress(buffer)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
guard let context = CGContext(data: data, width: width, height: height,
bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(buffer), space: rgbColorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)
else {
return nil
}
work(context)
CVPixelBufferUnlockBaseAddress(buffer, [])
return buffer
}
}
