Simplify the video deemphasis filter generation #479
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Previously this needed different hand-tuned scaling factors for PAL and NTSC. The missing bit was pre-warping the zero/pole frequencies to match the bilinear transform. The resulting filter is very close to the existing one (within 0.1dB for NTSC and 0.3dB for PAL), so this doesn't make much difference to the output.
happycube
approved these changes
Apr 9, 2020
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Previously this needed different hand-tuned scaling factors for PAL and NTSC. The missing bit was pre-warping the zero/pole frequencies to match the bilinear transform.
The resulting filter is very close to the existing one (within 0.1dB for NTSC and 0.3dB for PAL), so this doesn't make much difference to the output.
GNU Radio's implementation of FM (de)emphasis was a useful reference for this.
It might be possible to use the same helper function for the 75µs audio deemphasis as well?