setting the target level too high can produce broken output for exam

I think there are two issues at play here: An a

Fixed in v1.28.0, see <a class="issue-link js-issue-link" data-error-text="Failed to l

show warning when using non-default target level about ffmpeg-normalize HOT 5 CLOSED

milahu commented on August 17, 2024

show warning when using non-default target level

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Comments (5)

slhck commented on August 17, 2024

I think there are two issues at play here:

An apparently broken algorithm that is not fixed upstream (which seems to be worked on in some fork of FFmpeg, so it seems like that should be merged back into FFmpeg itself).
Usage notes that would help prevent issues from an end-user perspective.

What are you suggesting specifically? If "Going higher (> -14 LUFS) than source LUFS is forcing dynamic processing" (per the comment thread) then there could be a warning that dynamic mode is being used.

There is a warning already affecting the loudness range:

ffmpeg-normalize/ffmpeg_normalize/_streams.py

Lines 426 to 438 in 94c2c6a

 if ( 

 self.media_file.ffmpeg_normalize.loudness_range_target 

 < self.loudness_statistics["ebu"]["input_lra"] 

 and not will_use_dynamic_mode 

 ): 

 _logger.warning( 

 f"Input file had loudness range of {self.loudness_statistics['ebu']['input_lra']}. " 

 f"This is larger than the loudness range target ({self.media_file.ffmpeg_normalize.loudness_range_target}). " 

 "Normalization will revert to dynamic mode. Choose a higher target loudness range if you want linear normalization. " 

 "Alternatively, use the --keep-loudness-range-target or --keep-lra-above-loudness-range-target option to keep the target loudness range from " 

 "the input." 

 ) 

 will_use_dynamic_mode = True

Are you suggesting something akin to this?

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milahu commented on August 17, 2024

What are you suggesting specifically?

"show warning when using non-default target level"

if cli_args.target_level < -23:
    print(f"warning: using non-default target level {cli_args.target_level}. this can produce volume glitches. please verify the result.")

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slhck commented on August 17, 2024

I find this a bit too drastical. In your original issue you talked about increasing the target beyond the input loudness. I can imagine adding a warning for that.

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slhck commented on August 17, 2024

I did some checks on some files and it seems like the filter does not always revert to dynamic mode when the target is higher than the existing target. Instead, I'll parse the second pass loudnorm output and check if it shows that dynamic mode was used, compare that with the user's intent (i.e., if they wanted linear mode), and if there's a mismatch, print a warning.

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slhck commented on August 17, 2024

Fixed in v1.28.0, see #256

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	if (
	self.media_file.ffmpeg_normalize.loudness_range_target
	< self.loudness_statistics["ebu"]["input_lra"]
	and not will_use_dynamic_mode
	):
	_logger.warning(
	f"Input file had loudness range of {self.loudness_statistics['ebu']['input_lra']}. "
	f"This is larger than the loudness range target ({self.media_file.ffmpeg_normalize.loudness_range_target}). "
	"Normalization will revert to dynamic mode. Choose a higher target loudness range if you want linear normalization. "
	"Alternatively, use the --keep-loudness-range-target or --keep-lra-above-loudness-range-target option to keep the target loudness range from "
	"the input."
	)
	will_use_dynamic_mode = True