Hello everyone,
I'm a beginner starting to explore the libav librairies.
In order to understand how it works I've been trying to make a simple
transcoder which decode a video stream from my webcam and then re-encode it.
I'm currently using libavcodec 57. 96.101 / libavformat 57. 72.101 /
libavdevice 57. 7.100 . All taken from the git repository of FFmpeg.
I've successfully decoded the stream.
However when I try to use the avcodec_send_frame() function it results in a
segmentation fault.
I assume it's comming from a packet concept I haven't grasped yet or a bad
initialisation of my encoder.
Here is my encoding initialisation (skipping decoder, frame and packet
init):
...
AVCodec *p_encoder(NULL);
AVCodecContext *p_encoderContext(NULL);
...
p_encoder = avcodec_find_encoder(AV_CODEC_ID_MPEG2VIDEO );
if(!p_encoder)
return -1;
p_encoderContext = avcodec_alloc_context3(p_encoder);
if(!p_encoderContext)
return -1;
p_encoderContext->bit_rate = 300000;
p_encoderContext->width = p_decoderContext->width;
p_encoderContext->height = p_decoderContext->height;
p_encoderContext->time_base = (AVRational){1, 25};
p_encoderContext->framerate = (AVRational){25, 1};
p_encoderContext->gop_size = 10;
p_encoderContext->max_b_frames = 1;
p_encoderContext->pix_fmt = AV_PIX_FMT_YUV420P;
...
if (avcodec_open2(p_encoderContext, p_encoder, NULL) < 0)
return -1;
The loop where I read the frames :
while(av_read_frame(p_formatContext, p_inPkt) >= 0)
{
if(p_inPkt->stream_index == numStreamVideo)
{
if (p_inPkt->size)
{
decode(p_decoderContext, p_frameCam, p_inPkt, isDecoded);
av_packet_unref(p_inPkt);
}
cout << "Until here i'm good." << endl;
av_packet_unref(p_outPkt);
encode(p_encoderContext, p_frameCam, p_outPkt, nameFile);
}
}
My function encode() :
static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,
string nameFile)
{
int ret;
ret = avcodec_send_frame(enc_ctx, frame);
cout << ret << endl;
if(ret == AVERROR(EAGAIN))
{
cout << "BANG" << endl;
}
else if (ret < 0)
{
cout << "Error sending frame to encoding\n";
exit(1);
}
ret = avcodec_receive_packet(enc_ctx, pkt);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
{
cout << ".";
return;
}
else if (ret < 0)
{
cout << "Error during encoding\n";
exit(1);
}
SaveFrame(pkt, nameFile);
}
I've attached the source to this mail.
I hope you'll provide me some guidance to solve this segmentation fault
matter. Thank you beforehand and have a nice day!
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