Video recording

The GNOME Foundation has two video cameras we can use to record talks.

Currently one is with AlexandreFranke (Fr) and one is with SamThursfield (UK).

The cameras are Panasonic HC-W850 cameras. Here is the owner's manual and operating manual.

The venue has two radio microphones in each lecture, one handheld and one clip-on. The radio receivers each provide a line-level audio output at the front of the room.

Sam can get hold of two Zoom H4N audio recorders. The plan is to record the mic inputs at the front of the room into the Zoom recorders. The camera will be at the back of the room and will record audio using its internal mic. During post-processing we will need to combine the video and audio signals; as long as somebody claps at the start of each new segment of video and audio this should be simple enough.

Storage requirements

Uncompressed audio at 44KHz/16bit is ~10MB / minute (1), (2)

MP4/720p(9M) compressed video (1280x720 resolution) is ~720MB / minute (1).

The conference is 3 days x 8 hours over two rooms giving 2880 minutes of content in total.

Thus total storage requirements for recordings: 2880 * (720 + 10) = 2053GB -- we should aim to provide 4TB.

We have 2 x 64GB and 2 x 32GB SanDisk Ultra SDXC cards, Sam has them currently.

A 64GB SD card can hold around 90 minutes of video, or 109 hours of audio.

The talk rooms (G29 and G44) are free on Monday 24th July between 1pm – 3pm for us to do a test recording. We'll need at least one of the cameras by then.

Editing HOWTO

1. Download and open kdenlive video editor

2. TO DO: figure out people can get the unedited files easily from codething@

3. Create a new project, with:

  • 1080p resolution
  • 50 frames per second
  • 2 video tracks
  • 3 audio tracks

4. Import the video file -- go to "Project > Add clip" and select the video file. It will appear in the "Project bin".

5. Drag the clip from the "Project bin" to the Video 1 track

6. Look at the start and finish --- it may be that the talk is split across two files. Add the second clip if so and line it up with the first one in the same track.

7. Split out the camera audio, by right clicking the track and selecting "Split Audio"

8. Import the audio, again using "Add clip".

  • TO DO: kdenlive doesn't support splitting the stereo audio file into two separate channels, so we need to do that in advance

8. Sync the separate audio tracks with the camera audio. There may be a clapper board sound at the start, or you may have to use some other sound.

9. Mute the camera audio

10. Check the start and finish of the talk, and cut out unimportant bits

11. Check the audio during intro to the talk and the questions section; look for bits where a mic was on but nobody was speaking into it, and mute those parts.

12. Attach the intro and outro

13. Save the project

14. Click "Project > Render", select WebM format, and click "Render to file"

15. Copy the rendered .webm file to the backup server

16. Success!


GUADEC/2017/Video (last edited 2017-08-14 11:49:45 by SamThursfield)