Encoding raw YUV420P to h264 with AVCodec on iOS - ios

Question

I am trying to encode a single YUV420P image gathered from a CMSampleBuffer to an AVPacket so that I can send h264 video over the network with RTMP.
The posted code example seems to work as avcodec_encode_video2 returns 0 (Success) however got_output is also 0 (AVPacket is empty).
Does anyone have any experience with encoding video on iOS devices that might know what I am doing wrong?
- (void) captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection {
// sampleBuffer now contains an individual frame of raw video frames
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
// access the data
int width = CVPixelBufferGetWidth(pixelBuffer);
int height = CVPixelBufferGetHeight(pixelBuffer);
int bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
unsigned char *rawPixelBase = (unsigned char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
// Convert the raw pixel base to h.264 format
AVCodec *codec = 0;
AVCodecContext *context = 0;
AVFrame *frame = 0;
AVPacket packet;
//avcodec_init();
avcodec_register_all();
codec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (codec == 0) {
NSLog(#"Codec not found!!");
return;
}
context = avcodec_alloc_context3(codec);
if (!context) {
NSLog(#"Context no bueno.");
return;
}
// Bit rate
context->bit_rate = 400000; // HARD CODE
context->bit_rate_tolerance = 10;
// Resolution
context->width = width;
context->height = height;
// Frames Per Second
context->time_base = (AVRational) {1,25};
context->gop_size = 1;
//context->max_b_frames = 1;
context->pix_fmt = PIX_FMT_YUV420P;
// Open the codec
if (avcodec_open2(context, codec, 0) < 0) {
NSLog(#"Unable to open codec");
return;
}
// Create the frame
frame = avcodec_alloc_frame();
if (!frame) {
NSLog(#"Unable to alloc frame");
return;
}
frame->format = context->pix_fmt;
frame->width = context->width;
frame->height = context->height;
avpicture_fill((AVPicture *) frame, rawPixelBase, context->pix_fmt, frame->width, frame->height);
int got_output = 0;
av_init_packet(&packet);
avcodec_encode_video2(context, &packet, frame, &got_output)
// Unlock the pixel data
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
// Send the data over the network
[self uploadData:[NSData dataWithBytes:packet.data length:packet.size] toRTMP:self.rtmp_OutVideoStream];
}
Note: It is known that this code has memory leaks because I am not freeing the memory that is dynamically allocated.
UPDATE
I updated my code to use #pogorskiy method. I only try to upload the frame if got output returns 1 and clear the buffer once I am done encoding video frames.