|
|
| MrSmite |
| Posted: Jan 7 2012, 05:17 AM |
 |
|
Advanced Member
Group: Members
Posts: 102
Member No.: 25620
Joined: 30-May 09
|
After processing a video where I resampled the audio, I noticed a little "click" at the beginnng that is not
there in the original source.
These are the edits I performed:
1. Open a 3 second video which is nothing but black frames and silence with an audio track of 44100 Khz.
2. Append a video with the same specs.
3. Trim a few frames from where the two videos meet up to where the video fades in
4. Add a few video filters
5. Turn on advanced Audio Filtering
6. Add Input -> Resample -> Output
7. Set Resample to 48000 Khz with 128 taps
8. Process the video and the result is a video with artifacts in the sound track of the first three seconds which
were not there before the edit
Before:
After:
 [B]
Edit: Both before and after are uncompressed PCM and the source is a FRAPS video capture. I added a brightness filter for the screenshots only. |
|
| MrSmite |
| Posted: Jan 7 2012, 05:38 AM |
|
|
Advanced Member
Group: Members
Posts: 102
Member No.: 25620
Joined: 30-May 09
|
Followup:
I rendered the same video without cutting frames and it produced no artifacts. Also, scrubbing through
the edited version, the "click" is added exactly where the cut was.
The only way I could avoid the artifact was to render the video with Direct Stream Copy on the audio
while making my video edits, then render it again with advanced filtering on the audio and Direct Stream
Copy on the video. |
|
| phaeron |
| Posted: Jan 9 2012, 12:13 AM |
|
|
Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
|
I tried to reproduce this locally without success. Does this still happen if you export only the audio track (save wav), and are any of the video filters needed for it to happen?
|
|
| MrSmite |
| Posted: Jan 9 2012, 05:43 AM |
|
|
Advanced Member
Group: Members
Posts: 102
Member No.: 25620
Joined: 30-May 09
|
| QUOTE (phaeron @ Jan 9 2012, 12:13 AM) | | I tried to reproduce this locally without success. Does this still happen if you export only the audio track (save wav), and are any of the video filters needed for it to happen? |
Not sure, I'll try exporting the WAV and also with/without filters and post back in a couple days.
I'd give you the sources but the game recording is over 1GB because FRAPS is seimi-lossless. |
|
| MrSmite |
| Posted: Jan 14 2012, 05:30 AM |
|
|
Advanced Member
Group: Members
Posts: 102
Member No.: 25620
Joined: 30-May 09
|
Ok, so it appears to be a problem with the "Advanced Filtering" in the Audio.
Here are the two tests I did:
First Test
- Open / append the same videos as mentioned in the OP
- Cut a few overlapping frames at the join (about 50 from each side)
- Video Filters: None
- Video Compression: HuffYuv 2.1.1
- Audio: Checked "Use Advanced Filtering"
- Audio Filters: Input / Resample / Output
- Set "Resample" parameters: "Target Frequency 48000", "Taps 128" (also tried 127)
After exporting the WAV only, there was the "click" artifact as mentioned in the OP
Second Test
- All video procedures are the same as the "First Test"
- Audio: Unchecked "Use Advanced Filtering"
- Clicked "Conversion"
- Set "sampling rate 48000", checked "High Quality", left precision at 16, channels at stereo
After exporting the WAV only, the "click" artifact was not present
Note 1:
Both resulting WAV files were played in Winamp and MPC HomeCinema and the waveforms viewed in Cool Edit 2000 and Sony Vegas 7 to rule out the player as producing the artifact.
Note 2:
The artifact is placed exactly at the first join/cut. If you recall, the first video is 3 seconds with another appended to it. I cut frames from 2:59 to 3:01 (overlaping the join) and the artifact appears at 2.995 seconds in the new WAV, according to Cool Edit 2000.
Let me know if you need more info. |
|
| phaeron |
| Posted: Jan 17 2012, 12:36 AM |
|
|
Virtualdub Developer
Group: Administrator
Posts: 7773
Member No.: 61
Joined: 30-July 02
|
I think I might know where this is coming from now. Can you check the artifact in Cool Edit and see exactly what it is? If it's a single sample glitch, it's likely because of a lack of crossfading in the audio filter graph, so there is a discontinuity in the waveform. The old conversion filter runs across cuts and uses a lower quality filter that is more likely to reduce such artifacts (triangle filter).
|
|
| MrSmite |
| Posted: Jan 18 2012, 05:09 AM |
|
|
Advanced Member
Group: Members
Posts: 102
Member No.: 25620
Joined: 30-May 09
|
| QUOTE (phaeron @ Jan 17 2012, 12:36 AM) | | I think I might know where this is coming from now. Can you check the artifact in Cool Edit and see exactly what it is? If it's a single sample glitch, it's likely because of a lack of crossfading in the audio filter graph, so there is a discontinuity in the waveform. The old conversion filter runs across cuts and uses a lower quality filter that is more likely to reduce such artifacts (triangle filter). |
It does in fact seem to be that. In fact it's hardly noticeable on the waveform display without zooming it in (unless my ears are better than my eyes). |
|
