avcodec_receive_packet() doesn't see the output - ios

Question

I'm trying to create a converter which will make a video out of set of images. Everything is at its place, AVFormatContext, AVCodecContext, AVCodec. I'm creating YUV AVFrame out of UIImage and send it to encoder by avcodec_send_frame() method. Everything goes fine until I'm trying to get AVPacket with method avcodec_receive_packet(). Every time it returns -53 which means - output is not available in the current state - user must try to send input. As I said, I'm sending an input before I'm trying to get something and sending is successful.
Here's my code:
Init ffmpeg entities:
- (BOOL)setupForConvert:(DummyFVPVideoFile *)videoFile outputPath:(NSString *)path
{
if (!videoFile) {
[self.delegate convertationFailed:#"VideoFile is nil!"];
return NO;
}
currentVideoFile = videoFile;
outputPath = path;
BOOL success = NO;
success = [self initFormatCtxAndCodecs:path];
if (!success) {
return NO;
}
success = [self addCameraStreams:videoFile];
if (!success) {
return NO;
}
success = [self openIOContext:path];
if (!success) {
return NO;
}
return YES;
}
- (BOOL)initFormatCtxAndCodecs:(NSString *)path
{
//AVOutputFormat *fmt = av_guess_format("mp4", NULL, NULL);
int ret = avformat_alloc_output_context2(&pFormatCtx, NULL, NULL, [path UTF8String]);
if (ret < 0) {
NSLog(#"Couldn't create output context");
return NO;
}
//encoder codec init
pCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!pCodec) {
NSLog(#"Couldn't find a encoder codec!");
return NO;
}
pCodecCtx = avcodec_alloc_context3(pCodec);
if (!pCodecCtx) {
NSLog(#"Couldn't alloc encoder codec context!");
return NO;
}
pCodecCtx->codec_tag = AV_CODEC_ID_H264;
pCodecCtx->bit_rate = 400000;
pCodecCtx->width = currentVideoFile.size.width;
pCodecCtx->height = currentVideoFile.size.height;
pCodecCtx->time_base = (AVRational){1, (int)currentVideoFile.framerate};
pCodecCtx->framerate = (AVRational){(int)currentVideoFile.framerate, 1};
pCodecCtx->gop_size = 10;
pCodecCtx->max_b_frames = 1;
pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
NSLog(#"Couldn't open the encoder codec!");
return NO;
}
pPacket = av_packet_alloc();
return YES;
}
- (BOOL)addCameraStreams:(DummyFVPVideoFile *)videoFile
{
AVCodecParameters *params = avcodec_parameters_alloc();
if (!params) {
NSLog(#"Couldn't allocate codec parameters!");
return NO;
}
if (avcodec_parameters_from_context(params, pCodecCtx) < 0) {
NSLog(#"Couldn't copy parameters from context!");
return NO;
}
for (int i = 0; i < videoFile.idCameras.count - 1; i++)
{
NSString *path = [videoFile.url URLByAppendingPathComponent:videoFile.idCameras[i]].path;
AVStream *stream = avformat_new_stream(pFormatCtx, pCodec);
if (!stream) {
NSLog(#"Couldn't alloc stream!");
return NO;
}
if (avcodec_parameters_copy(stream->codecpar, params) < 0) {
NSLog(#"Couldn't copy parameters into stream!");
return NO;
}
stream->avg_frame_rate.num = videoFile.framerate;
stream->avg_frame_rate.den = 1;
stream->codecpar->codec_tag = 0; //some silly workaround
stream->index = i;
streams[path] = [[VideoStream alloc] initWithStream:stream];
}
return YES;
}
- (BOOL)openIOContext:(NSString *)path
{
AVIOContext *ioCtx = nil;
if (avio_open(&ioCtx, [path UTF8String], AVIO_FLAG_WRITE) < 0) {
return NO;
}
pFormatCtx->pb = ioCtx;
return YES;
}
And here's convertation process:
- (void)launchConvert:(DummyFVPVideoFile *)videoFile
{
BOOL convertInProgress = YES;
unsigned int frameCount = 1;
unsigned long pts = 0;
BOOL success = NO;
success = [self writeHeader];
if (!success) {
NSLog(#"Couldn't write header!");
return;
}
AVRational defaultTimeBase;
defaultTimeBase.num = 1;
defaultTimeBase.den = videoFile.framerate;
AVRational streamTimeBase = streams.allValues.firstObject.stream->time_base;
while (convertInProgress)
{
pts += av_rescale_q(1, defaultTimeBase, streamTimeBase);
for (NSString *path in streams.allKeys)
{
UIImage *img = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:#"%#/%u.jpg", path, frameCount]];
AVPacket *pkt = [self getAVPacket:img withPts:pts];
if (!pkt->data) { continue; }
pkt->stream_index = streams[path].stream->index;
//check all settings of pkt
if (![self writePacket:pkt]) {
NSLog(#"Couldn't write packet!");
convertInProgress = NO;
break;
}
}
frameCount++;
}
success = [self writeTrailer];
if (!success) {
NSLog(#"Couldn't write trailer!");
return;
}
NSLog(#"Convertation finished!");
//delegate convertationFinished method
}
- (BOOL)writeHeader
{
if (avformat_write_header(pFormatCtx, NULL) < 0) {
return NO;
}
return YES;
}
- (BOOL)writePacket:(AVPacket *)pkt
{
if (av_interleaved_write_frame(pFormatCtx, pkt) != 0) {
return NO;
}
return YES;
}
- (BOOL)writeTrailer
{
if (av_write_trailer(pFormatCtx) != 0) {
return NO;
}
return YES;
}
/**
This method will create AVPacket out of UIImage.
#return AVPacket
*/
- (AVPacket *)getAVPacket:(UIImage *)img withPts:(unsigned long)pts
{
if (!img) {
NSLog(#"imgData is nil!");
return nil;
}
uint8_t *imgData = [self getPixelDataFromImage:img];
AVFrame *frame_yuv = av_frame_alloc();
if (!frame_yuv) {
NSLog(#"frame_yuv is nil!");
return nil;
}
frame_yuv->format = AV_PIX_FMT_YUV420P;
frame_yuv->width = (int)img.size.width;
frame_yuv->height = (int)img.size.height;
int ret = av_image_alloc(frame_yuv->data,
frame_yuv->linesize,
frame_yuv->width,
frame_yuv->height,
frame_yuv->format,
32);
if (ret < 0) {
NSLog(#"Couldn't alloc yuv frame!");
return nil;
}
struct SwsContext *sws_ctx = nil;
sws_ctx = sws_getContext((int)img.size.width, (int)img.size.height, AV_PIX_FMT_RGB24,
(int)img.size.width, (int)img.size.height, AV_PIX_FMT_YUV420P,
0, NULL, NULL, NULL);
const uint8_t *scaleData[1] = { imgData };
int inLineSize[1] = { 4 * img.size.width };
sws_scale(sws_ctx, scaleData, inLineSize, 0, (int)img.size.height, frame_yuv->data, frame_yuv->linesize);
frame_yuv->pict_type = AV_PICTURE_TYPE_I;
frame_yuv->pts = pCodecCtx->frame_number;
ret = avcodec_send_frame(pCodecCtx, frame_yuv); //every time everything is fine
if (ret != 0) {
NSLog(#"Couldn't send yuv frame!");
return nil;
}
av_init_packet(pPacket);
pPacket->dts = pPacket->pts = pts;
do {
ret = avcodec_receive_packet(pCodecCtx, pPacket); //every time -35 error
NSLog(#"ret = %d", ret);
if (ret == AVERROR_EOF) {
NSLog(#"AVERROR_EOF!");
} else if (ret == AVERROR(EAGAIN)) {
NSLog(#"AVERROR(EAGAIN)");
} else if (ret == AVERROR(EINVAL)) {
NSLog(#"AVERROR(EINVAL)");
}
if (ret != 0) {
NSLog(#"Couldn't receive packet!");
//return nil;
}
} while ( ret == 0 );
free(imgData);
av_packet_unref(pPacket);
av_packet_free(pPacket);
av_frame_unref(&frame_yuv);
av_frame_free(&frame_yuv);
//perform other clean up and test dat shit
return pPacket;
}
Any insights would be helpful. Thanks!

Answer 1

There may be two reasons.
According to on of the documents of FFmpeg you may need to feed more then one packet to avcodec_send_frame() to receive packet return successful.
I cannot confirm that you allocated enough sized buffer for pPacket. The functions av_packet_alloc() and av_init_packet() won't allocate any buffer but latter sets it to NULL instead. So allocation must be done after init. Somewhere you should allocate buffer either manually or with av_new_packet(pPacket, SIZE).
Hope that helps.