use VideoWriterFile to save video file but do not save stream

[logici]

Description

I want to save video stream as a file.I use OpenVideoCapture to get camera stream and use VideoWriter to save .

Steps to Reproduce

func main() {
	// set to use a video capture device 0
	deviceID := 0

	// open webcam
	webcam, err := gocv.OpenVideoCapture(deviceID)
	if err != nil {
		fmt.Println(err)
		return
	}
	defer webcam.Close()

	// open display window
	window := gocv.NewWindow("Test")
	defer window.Close()

	// prepare image matrix
	img := gocv.NewMat()
	defer img.Close()

	fmt.Printf("start reading camera device: %v\n", deviceID)
	fps := 25.0
	filename := "./live.avi"
	var writer *gocv.VideoWriter
	isColor := true
	codec := "h264"
	//fmt.Println("%d", img.Size()[0])
	writer, err = gocv.VideoWriterFile(filename, codec, float64(fps), 720, 1280, isColor)
	defer writer.Close()
	if err != nil {
		fmt.Println(err)
		return
	}
	if !writer.IsOpened() {
		fmt.Println("Could not open the output video file for write")
		return
	}
	for {
		if ok := webcam.Read(&img); !ok {
			fmt.Printf("cannot read device %v\n", deviceID)
			return
		}
		if img.Empty() {
			continue
		}
		err := writer.Write(img)
		if err != nil {
			fmt.Println(err)
			return
		}

		// show the image in the window, and wait 1 millisecond
		window.IMShow(img)
		if window.WaitKey(5) > 0 {
			break
		}
	}
	return
}

there was not any error my compiler reported.But the live.avi file do not play and no stream data. use ffmpeg command to get live.avi info.

ffprobe -v 0 ./live.avi -print_format json -show_format -show_streams

{
    "streams": [
        {
            "index": 0,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "codec_type": "video",
            "codec_time_base": "1/50",
            "codec_tag_string": "h264",
            "codec_tag": "0x34363268",
            "width": 720,
            "height": 1280,
            "coded_width": 720,
            "coded_height": 1280,
            "has_b_frames": 0,
            "level": -99,
            "chroma_location": "left",
            "refs": 1,
            "is_avc": "false",
            "nal_length_size": "0",
            "r_frame_rate": "25/1",
            "avg_frame_rate": "25/1",
            "time_base": "1/25",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 0,
            "duration": "0.000000",
            "disposition": {
                "default": 0,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            }
        }
    ],
    "format": {
        "filename": "./live.avi",
        "nb_streams": 1,
        "nb_programs": 0,
        "format_name": "avi",
        "format_long_name": "AVI (Audio Video Interleaved)",
        "start_time": "0.000000",
        "size": "5686",
        "probe_score": 100,
        "tags": {
            "encoder": "Lavf58.29.100"
        }
    }
}

and play it

ffplay ./live.avi

[avi @ 0x7ff1f186e600] Could not find codec parameters for stream 0 (Video: h264 (h264 / 0x34363268), none, 720x1280): unspecified pixel format
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, avi, from './live.avi':
  Metadata:
    encoder         : Lavf58.29.100
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: h264 (h264 / 0x34363268), none, 720x1280, 25 fps, 25 tbr, 25 tbn, 50 tbc
    nan M-V:    nan fd=   0 aq=    0KB vq=    0KB sq=    0B f=0/0   

Your Environment

my environment is: gocv version: 0.23.0 opencv lib version: 4.3.0 macOs10 I use brew install opencv to install OpenCV

What happen for my code ? what should I do?

[skytodmoon]

The same problem, we want to cast a video stream by rtmp or rtsp like opencv, any suggenstions?

[Raggaer]

Having the same problem here

[abdurrahmanekr]

I was having this problem too and then I realized that the resolution of the image should be the same as the VideoWriterFile resolution.

writer, err := gocv.VideoWriterFile("video.mp4", "avc1", float64(25), 1280, 720, true)

img := gocv.IMRead("/path/to/image", gocv.IMReadColor)
resized := gocv.NewMat()
gocv.Resize(img, &resized, image.Pt(1280, 720), 0, 0, gocv.InterpolationArea)

writer.Write(resized)

writer.Close()

Actually the library didn't warn me, it would be nice if an improvement was made about it.