CODEWITHSUNDEEP
c++encodingopencvffmpeglibx264
user573193
user573193

Reputation: 31

X264 encoding using Opencv

I am working with a high resolution camera: 4008x2672. I a writing a simple program which grabs frame from the camera and sends the frame to a avi file. For working with such a high resolution, I found only x264 codec that could do the trick (Suggestions welcome). I am using opencv for most of the image handling stuff. As mentioned in this post http://doom10.org/index.php?topic=1019.0 , I modified the AVCodecContext members as per ffmpeg presets for libx264 (Had to do this to avoid broken ffmpeg defaults settings error). This is output I am getting when I try to run the program

libx264 @ 0x992d040]non-strictly-monotonic PTS 
1294846981.526675 1 0 //Timestamp camera_no frame_no
1294846981.621101 1 1
1294846981.715521 1 2
1294846981.809939 1 3
1294846981.904360 1 4
1294846981.998782 1 5
1294846982.093203 1 6
    Last message repeated 7 times
[avi @ 0x992beb0]st:0 error, non monotone timestamps 
-614891469123651720 >= -614891469123651720

 OpenCV Error: Unspecified error (Error while writing video frame) in
 icv_av_write_frame_FFMPEG, file 
/home/ajoshi/ext/OpenCV-2.2.0/modules/highgui/src/cap_ffmpeg.cpp, line 1034
terminate called after throwing an instance of 'cv::Exception'
 what():  /home/ajoshi/ext/OpenCV-2.2.0/modules/highgui/src/cap_ffmpeg.cpp:1034:
error: (-2) Error while writing video frame in function icv_av_write_frame_FFMPEG

Aborted

Modifications to the AVCodecContext are:

if(codec_id == CODEC_ID_H264)
{
    //fprintf(stderr, "Trying to parse a preset file for libx264\n");
    //Setting Values manually from medium preset
    c->me_method = 7;
    c->qcompress=0.6;
    c->qmin = 10;
    c->qmax = 51;
    c->max_qdiff = 4;
    c->i_quant_factor=0.71;
    c->max_b_frames=3;
    c->b_frame_strategy = 1;
    c->me_range = 16;<br>
    c->me_subpel_quality=7;
    c->coder_type = 1;
    c->scenechange_threshold=40;
    c->partitions = X264_PART_I8X8 | X264_PART_I4X4 | X264_PART_P8X8 | X264_PART_B8X8;
    c->flags = CODEC_FLAG_LOOP_FILTER;
    c->flags2 = CODEC_FLAG2_BPYRAMID | CODEC_FLAG2_MIXED_REFS | CODEC_FLAG2_WPRED | CODEC_FLAG2_8X8DCT | CODEC_FLAG2_FASTPSKIP;
    c->keyint_min = 25;
    c->refs = 3;
    c->trellis=1;
    c->directpred = 1;
    c->weighted_p_pred=2;
}

I am probably not setting the dts and pts values which I believed ffmpeg should be setting it for me.

Any sugggestions welcome.
Thanks in advance

Upvotes: 3

Views: 6272

Answers (3)

Asad R.
Asad R.

Reputation: 1051

The pts value of the AVFrame you send as the last argument to avcodec_encode_video needs to be set by you. Once you set this, the codec context's coded_from->pts field will have the correct value which you can av_rescale_q() and set in the AVPacket for your av_interleaved_write_frame().

Upvotes: 0

9dan
9dan

Reputation: 4282

Actual error is "non monotone timestamps". I seems that you didn't properly initialized video frame properties. If its possible use libx264 directly. It'll be more easy to handle.

PS. you can work around ffmpeg x264 setting problem by specify 264 preset file with -fvpre option.

Upvotes: 1

Martin Beckett
Martin Beckett

Reputation: 96167

I would probably run the x264 executable in another process and pipe either rgb or yuv pixels to it. Then you can use all the normal x264 (or ffmpeg) flags and it handles multi threading for you.

And since x264 is GPL licensed it also gives you more freedom on licensing your app.

ps. Here is some sample code using ffmpeg from Qt you can ignore the Qt specific bits but it gives a good starting point for using ffmpeg from a c++ app.

Upvotes: 2

Related Questions