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Topic: Detecting Preset From Lame Tag? (Read 2257 times) previous topic - next topic
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Detecting Preset From Lame Tag?

Can the preset used be detected from the lame tag?

Here's what I currently use to detect alt-preset standard, extreme, insane and not alt-preset:

  # Classify this mp3 based on the tag values.
  # Rules:
  #  noiseshaping is 2 in both aps and apx
  #  it is 1 in api
  #  quality is 78 in aps and apx
  #  58 in api
  #  nspytune is used as the PychcoAcousticModel in all three alt presets
  #  lowpass filter aps:19000 apx:19500 api:20500
  #  vbr mode in aps and apx is vbr-old/vbr-rh
  #  vbr mode in api is cbr
  #  that is, both aps and apx have for vbr mode: vbr-old/vbr-rh
  #  there are definite red flags though that an mp3 was not encoded with an alt preset
  #  This is a no-no: ath type 3, vbr method vbr-mtrh
  #  anything with either of those settings is not an alt preset file
  #  always joint stereo
  #  api is joint stereo as well
  #  API is jstereo.  If it wasnt, then the mp3 would be forced at 160kbps per channel all the time irregardless of the complexity of the music
  #  all three use -ns-safejoint

  def classify
    if ath_type == 3 || vbr_method == "vbr-mtrh"
      return "not alt-preset"
    end
    if stereo_mode == "joint" && safejoint
      if noise_shaping == 2 && vbr_quality == 78 && vbr_method == "vbr-old / vbr-rh"
   if lowpass_filter == 19000
     return "APS"
   elsif lowpass_filter == 19500
     return "APX"
   end
      elsif noise_shaping == 1 && vbr_quality == 58 &&
     vbr_method == "no vbr / cbr" && lowpass_filter == 20500
   return "API"
      end
    else
      "not alt-preset"
    end
  end

Could low-quality encoded mp3's slip through this logic? Any detailed info on the actual settings used for each preset?

Detecting Preset From Lame Tag?

Reply #1 –
sorry that the formatting was messed up. Don't know how to bypass the forum software...

Detecting Preset From Lame Tag?

Reply #2 –
I always thought ap fast used vbr-mtrh. But you mean it uses vbr-rh?
 

Detecting Preset From Lame Tag?

Reply #3 –
No, thats probably a problem with my rules here. the "fast" settings are detected as "not alt-presets".

Do you know someplace to get a complete list of the actual settings for each preset?