Hqdn3d's documentation recommends not using values greater than 10 for the luma_spatial and chroma_spatial and than 13 for luma_tmp and chroma_tmp. For this reason, it is better to use conservative values for the denoiser. Remember that fine details, such as hair or wrinkles, may be mistaken for video noise and subsequently removed by the filter. To remove the grain and video defects, the video is smoothed and can become blurry if an aggressive filter is used ( Figure 3). luma_tmp and chroma_tmp describe the treatment of noise that shows up through multiple frames.ĭenoising is a destructive action. luma_spatial and chroma_spatial affect the dissipation of static noise (the noise that is analyzed in each frame without taking other frames into account). These parameters are luma_spatial, chroma_spatial, luma_tmp, and chroma_tmp. Hqdn3d accepts four different parameters that regulate its aggressiveness. I used the high-quality denoise 3D (hqdn3d) filter in Listing 3. Unless your source material is very high quality with no noticeable defects, applying a denoiser video filter to your captured file might be a good idea. This video noise makes the file more difficult to compress with video encoders and delivers poor output quality, as well. VHS tapes often contain grainy artifacts. Listing 3 transcodes the captured video file and the cleaned audio file into vhs_final.mkv. Start and end positions are values in the form hours:minutes:seconds, such as 01:30:50. However, I used FFmpeg in my example, because it is easily available and well documented.įor the excess video usually found at the beginning and end of a recording, trim it out with the following command: ffmpeg -i vhs_whole.mkv -acodec copy -vcodec copy -ss $start_position -to $end_position vhs_trim.mkv This file may be transcoded into some more practical format using any encoder, such as HandBrake or MEncoder. You now have a video file with clean audio that uses about 15GB of disk space. Then this video stream is combined with the clean version of the audio just generated, and the whole file is stored as vhs_whole.mkv: ffmpeg -i vhs.mkv -vcodec copy -an vhs_video_only.mkvįfmpeg -i vhs_video_only.mkv -i vhs_tmpaud-clean.wav -map 0:v -map 1:a -c:v copy -c:a copy vhs_whole.mkv The Transcoding Process In this example, a video-only stream is extracted from vhs.mkv and stored in vhs_video_only.mkv. Values between 0.21 and 0.31 are reasonable.įinally, the audio is muxed back with the video stream. Values that are too high will cause audible sound artifacts that are in fact worse than the original noise. Denoising is a destructive procedure that may wipe information away. Higher values mean more noise reduction, but at the expense of sound fidelity. The last value of the sox command above defines the denoiser's aggressiveness. Sox vhs_tmpaud.wav vhs_tmpaud-clean.wav noisered general_noise.prof 0.21Ī clean version of the audio will be recorded to vhs_tmpaud-clean.wav. Now, the tape's digitized audio can be extracted from its file and cleaned with: ffmpeg -i vhs.mkv -acodec pcm_s16le -vn vhs_tmpaud.wav This profile can be used for reducing the noise in the audio you capture. This will create a file named noiseprofile that contains a description of the noise introduced by Eas圜AP. With your Eas圜AP connected to the VCR when it is not generating any sound output (e.g., when the tape is paused), capture a few seconds of an audio segment as follows: gst-launch-1.0 -q alsasrc device=$alsadevice ! wavenc ! fdsink | sox -t wav -n trim 0 1 noiseprof noiseprofile First, capture an audio segment that only contains the noise introduced by the capture card. You can further narrow the field of equalization by dragging the top-left plot mark a little to the right and the top-right plot mark a little to left.To mitigate the noise introduced by the capture card, you can use SoX. Drag this mark to the right if you can still hear a “low-pitched sound. The equalization line should look like a flat line with a dip near the end Step 8Ĭlick “Preview” to review how much you’ve reduced the sound Step 9ĭrag the bottom plot mark to the left if you can still hear a “high-pitched” metallic sound. In the Equalization dialogue box, double-click around 8 kilohertz on the equalization line to insert a plot mark Step 6ĭouble-click on 7 kilohertz and 9 kilohertz to create two more plot marks Step 7Ĭlick and hold the 8 kilohertz plot mark and drag the mark down do the -24 dB level. Once you have located the section, click “Stop” Step 3ĭrag the cursor over the part with the metallic sound to highlight Step 4Ĭlick “Edit” and select “Equalization” Step 5 Step 2Ĭlick “Play” and locate the section with the metallic, tin-like sound. Open Audacity, click “File” and “Open” and locate the file you want to fix.
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