SlideShare a Scribd company logo
1 of 25
Download to read offline
The Secret Lives
     of MP3 Files

        Doug Kaye
The Conversations Network
    and GigaVox Media
Formats & Encoders

  • Lossless (WAV, AIFF)
  • Lossy
   - MPEG 1, Layer 3 (MP3)
   - AAC (AAC, M4A, M4B)
   - MPEG I, Layer 2 (MP2)
MPEG Confusion


• Lossy Perceptual/Psychoacoustical Codecs
• MP3 = MPEG-I Layer 3
• MP2 = MPEG-I Layer 2 (not MPEG-II)
Motion Picture Experts Group

   • MPEG-1:Video CDs, MP3 Audio
   • MPEG-2: Digital TV, Set-Top Boxes
   • MPEG-4: Online Multimedia (Video)
   • MPEG-7: Audio and Video Search
   • MPEG-21: Multimedia Framework
MPEG-1 for Geeks
• Layer 1
 • Simple 32-Band Algorithm
 • Philips DCC (Digital Compact Cassette)
• Layer 2 (a.k.a. MUSICAM)
 • Also 32 Bands
 • International Standard for Broadcasting
MPEG-1 Layer 3 (MP3)
    for Geeks
• Psychoacoustic Masking
 • 32 Bands Divided into 576 Subbands
 • More Accurate Masking Thresholds
• Redundancy Reduction
 • Lossless Huffman Encoding
• Bit-Reservoir Buffering
• Joint Stereo
Sample Rate for Geeks

• The Nyquist Theorem
 • Sample at 2x the Highest Frequency
 • 22.05kHz Sample Rate for 11kHz Audio
• Sample Rate Is aSource (WAV or AIFF)
                   Property of
  Uncompressed
Sample Rate in Practice

• Standardize on 44.1kHz Sample Rate
• Flash & Other Players Require n*11.025kHz
• Resample if Source is 48kHz from DVDs
Bit Rate for Geeks
• Independent of Sample Rate
• Specifies Encoder Output File Size (CBR)
 • @64kbps, 1 hour ≈ 27MB
• Variable Bit Rate (VBR)
 • For Higher Bit Rates Only
 • Not Universally Supported (Avoid It)
Bit Rate in Practice
• “Use Higher Bit Rates for Music?”
• It’s a Myth!
 • Human Voices Are Complex
 • Music Masks Its Own Artifacts
• 64kbps is Most Common Today
• 96kbps is Gaining
Podcasting Bit-Rate History

  • June 2003: 32kbps. “Files too large”
  • April 2004: 48kbps. “No problem”
  • September 2004: 64kbps. “Quality is low”
  • Today: Still 64kbps.
  • Tomorrow??
Stereo Encoding

• “Stereo MP3s are twice as large as mono.”
• It’s a Myth!
• Only Bit Rate Specifies Output File Size
• You May Want to Use Higher Bit Rates for Stereo
Stereo Encoding for Geeks

  • Dual Channel or Independent Channel (IC)
   - Entirely Separate Left and Right
  • But Most L/R Information is Redundant
  • Intensity Stereo (IS)
  • Mid/Side Stereo (MS)
  • Joint Stereo (JS) Allows IS/MS Combination
Stereo Encoding
       (Even Geekier)

• JS Encodes L+R and L-R
• If L=R then L-R=0
• SinceUsesRate is ConstantStereo Information
        Bit
  L=R       Fewer Bits for
Stereo Encoding in Practice

  • StereoReason to (not Music vs.Voice) is a
           vs. Mono
    Good             Use Higher Bit Rates
  • Greater Separation Suggests Higher Rates
  • If Mostly Speech, Consider 100% Mono
  • If Mono, Make L&R Digitally Identical
  • Always Encode in Stereo for Compatibility
Mastering for MP3

• Help the Encoder: Eliminate Unnecessary Data
 - High-Pass Filter at 80Hz
 - Low-Pass Filter at 11kHz (@64kbps encoding)
 - Normalize
Which is Louder?




• It’s Not the Height of the Peaks (voltage)
• It’s the Area Under the Curve (power)
Loudness
• What’s the Standard?
• We Asked:
 - Podcasters
 - Audio Engineers
 - Radio Engineers
• Answer: There Isn’t One
• It’s a Hard Problem to Solve
Normalization

• Peak Normalization (common)
 - Maximizes Voltage, not Power
• RMS Normalization
 - Maximizes Power (=Loudness)
• Determine a Standard Loudness Level
Avoid Recording to MP3!

• MP3 is a final/release format.
• Not designed to be decoded and re-encoded.
• Use MP2 Instead...
• or the highest MP3 bit rate possible.
AAC/M4B Files?

• Yes, AAC is Better Than MP3
• We Added AAC to Support iPod Bookmarks
• Painful: Only iTunes Could Encode M4B
• Doubled Much of Our Workflow
• Can’t Be Easily Assembled
MP2: Why and When?

• MPEG-1 Layer 2
• Designed as an Intermediate Format
• The Standard in Broadcast Radio
• 128kbps per Track
• 44.1kHz Sample Rate Preferred
Audio Lessons Learned

• MP3 Options
• Audio-File Myths
• RMS Normalization (Loudness)
• AAC/M4B Files (iTunes & iPods)
• MP2 Files
To Summarize
• Record at 44.1kHz Sample Rate (not in MP3!)
• Mastering
 - RMS Normalization (Pick a Standard Level)
 - 80Hz Hi-Pass, 11kHz Low Pass (for voice)
 - If Mono, Make L&R Digitally Identical
• Encoding
 - 64kbps when L=R
 - Consider ≥96kbps for L≠R
 - Always Use Joint Stereo
The Secret Lives of MP3 Files

More Related Content

Similar to The Secret Lives of MP3 Files

Aac nero compression optimization
Aac nero compression optimizationAac nero compression optimization
Aac nero compression optimization
Sevana Oü
 
Mp3 lame bitrate compression optimization
Mp3 lame bitrate compression optimizationMp3 lame bitrate compression optimization
Mp3 lame bitrate compression optimization
Sevana Oü
 
Mp3 ogg aac bitrate size quality compression optimization
Mp3 ogg aac bitrate size quality compression optimizationMp3 ogg aac bitrate size quality compression optimization
Mp3 ogg aac bitrate size quality compression optimization
Sevana Oü
 
3 multimedia elements - audio
3   multimedia elements - audio3   multimedia elements - audio
3 multimedia elements - audio
Kelly Bauer
 
Compression presentation 415 (1)
Compression presentation 415 (1)Compression presentation 415 (1)
Compression presentation 415 (1)
Godo Dodo
 
Encoding for i devices
Encoding for i devicesEncoding for i devices
Encoding for i devices
cakogal
 

Similar to The Secret Lives of MP3 Files (20)

Aac nero compression optimization
Aac nero compression optimizationAac nero compression optimization
Aac nero compression optimization
 
Mp3 lame bitrate compression optimization
Mp3 lame bitrate compression optimizationMp3 lame bitrate compression optimization
Mp3 lame bitrate compression optimization
 
Mp3 ogg aac bitrate size quality compression optimization
Mp3 ogg aac bitrate size quality compression optimizationMp3 ogg aac bitrate size quality compression optimization
Mp3 ogg aac bitrate size quality compression optimization
 
Audio Mastering
Audio MasteringAudio Mastering
Audio Mastering
 
History of digital week4
History of digital week4History of digital week4
History of digital week4
 
Audio format ict
Audio format ictAudio format ict
Audio format ict
 
Skype for Interviews
Skype for InterviewsSkype for Interviews
Skype for Interviews
 
Audio Compression_2023.pptx
Audio Compression_2023.pptxAudio Compression_2023.pptx
Audio Compression_2023.pptx
 
audio-production-1231352387673755-2.ppt
audio-production-1231352387673755-2.pptaudio-production-1231352387673755-2.ppt
audio-production-1231352387673755-2.ppt
 
CHAPTER – 5 Audio
CHAPTER – 5     AudioCHAPTER – 5     Audio
CHAPTER – 5 Audio
 
Mp3 And Mp4
Mp3 And Mp4Mp3 And Mp4
Mp3 And Mp4
 
3 multimedia elements - audio
3   multimedia elements - audio3   multimedia elements - audio
3 multimedia elements - audio
 
Compression presentation 415 (1)
Compression presentation 415 (1)Compression presentation 415 (1)
Compression presentation 415 (1)
 
Audio compression
Audio compressionAudio compression
Audio compression
 
audiocompression-130624061221-phpapp02.pptx
audiocompression-130624061221-phpapp02.pptxaudiocompression-130624061221-phpapp02.pptx
audiocompression-130624061221-phpapp02.pptx
 
Audio compression
Audio compressionAudio compression
Audio compression
 
Encoding for i devices
Encoding for i devicesEncoding for i devices
Encoding for i devices
 
Compressing Audio and Video for Desktop and Mobile Delivery
Compressing Audio and Video for Desktop and Mobile DeliveryCompressing Audio and Video for Desktop and Mobile Delivery
Compressing Audio and Video for Desktop and Mobile Delivery
 
Digital Audio in Multimedia
Digital Audio in MultimediaDigital Audio in Multimedia
Digital Audio in Multimedia
 
Chapter Seven
Chapter SevenChapter Seven
Chapter Seven
 

Recently uploaded

Prezentacja Q1 2024 EN strona www relacji
Prezentacja Q1 2024  EN strona www relacjiPrezentacja Q1 2024  EN strona www relacji
Prezentacja Q1 2024 EN strona www relacji
klaudiafilka
 
TriStar Gold- 05-13-2024 corporate presentation
TriStar Gold- 05-13-2024 corporate presentationTriStar Gold- 05-13-2024 corporate presentation
TriStar Gold- 05-13-2024 corporate presentation
Adnet Communications
 
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
atedyxc
 
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
atedyxc
 
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
atedyxc
 
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
atedyxc
 
Rapport annuel de Encevo Group pour l'année 2023
Rapport annuel de Encevo Group pour l'année 2023Rapport annuel de Encevo Group pour l'année 2023
Rapport annuel de Encevo Group pour l'année 2023
Paperjam_redaction
 
DSP Gold ETF Fund of Fund PPT - April'2024
DSP Gold ETF Fund of Fund PPT - April'2024DSP Gold ETF Fund of Fund PPT - April'2024
DSP Gold ETF Fund of Fund PPT - April'2024
DSP Mutual Fund
 
Zepto Case study(On Track to Profitability).pptx
Zepto Case study(On Track to Profitability).pptxZepto Case study(On Track to Profitability).pptx
Zepto Case study(On Track to Profitability).pptx
aryan963438
 
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
atedyxc
 

Recently uploaded (20)

What exchange can I sell my pi coins in 2024
What exchange can I sell my pi coins in 2024What exchange can I sell my pi coins in 2024
What exchange can I sell my pi coins in 2024
 
Prezentacja Q1 2024 EN strona www relacji
Prezentacja Q1 2024  EN strona www relacjiPrezentacja Q1 2024  EN strona www relacji
Prezentacja Q1 2024 EN strona www relacji
 
TriStar Gold- 05-13-2024 corporate presentation
TriStar Gold- 05-13-2024 corporate presentationTriStar Gold- 05-13-2024 corporate presentation
TriStar Gold- 05-13-2024 corporate presentation
 
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
一比一原版(UPenn毕业证书)宾夕法尼亚大学毕业证成绩单学位证书
 
Pitch-deck CopyFinancial and MemberForex.ppsx
Pitch-deck CopyFinancial and MemberForex.ppsxPitch-deck CopyFinancial and MemberForex.ppsx
Pitch-deck CopyFinancial and MemberForex.ppsx
 
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
一比一原版(UC Davis毕业证书)加州大学戴维斯分校毕业证成绩单学位证书
 
The Pfandbrief Roundtable 2024 - Covered Bonds
The Pfandbrief Roundtable 2024 - Covered BondsThe Pfandbrief Roundtable 2024 - Covered Bonds
The Pfandbrief Roundtable 2024 - Covered Bonds
 
Managing personal finances wisely for financial stability and
Managing personal finances wisely for financial stability  andManaging personal finances wisely for financial stability  and
Managing personal finances wisely for financial stability and
 
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
一比一原版(Cornell毕业证书)康奈尔大学毕业证成绩单学位证书
 
NO1 Top Vashikaran Specialist in Uk Black Magic Specialist in Uk Black Magic ...
NO1 Top Vashikaran Specialist in Uk Black Magic Specialist in Uk Black Magic ...NO1 Top Vashikaran Specialist in Uk Black Magic Specialist in Uk Black Magic ...
NO1 Top Vashikaran Specialist in Uk Black Magic Specialist in Uk Black Magic ...
 
1. Elemental Economics - Introduction to mining
1. Elemental Economics - Introduction to mining1. Elemental Economics - Introduction to mining
1. Elemental Economics - Introduction to mining
 
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
一比一原版(Caltech毕业证书)加利福尼亚理工学院毕业证成绩单学位证书
 
20240514-Calibre-Q1-2024-Conference-Call-Presentation.pdf
20240514-Calibre-Q1-2024-Conference-Call-Presentation.pdf20240514-Calibre-Q1-2024-Conference-Call-Presentation.pdf
20240514-Calibre-Q1-2024-Conference-Call-Presentation.pdf
 
Production and Cost of the firm with curves
Production and Cost of the firm with curvesProduction and Cost of the firm with curves
Production and Cost of the firm with curves
 
Diversification in Investment Portfolio.pdf
Diversification in Investment Portfolio.pdfDiversification in Investment Portfolio.pdf
Diversification in Investment Portfolio.pdf
 
Rapport annuel de Encevo Group pour l'année 2023
Rapport annuel de Encevo Group pour l'année 2023Rapport annuel de Encevo Group pour l'année 2023
Rapport annuel de Encevo Group pour l'année 2023
 
DSP Gold ETF Fund of Fund PPT - April'2024
DSP Gold ETF Fund of Fund PPT - April'2024DSP Gold ETF Fund of Fund PPT - April'2024
DSP Gold ETF Fund of Fund PPT - April'2024
 
Zepto Case study(On Track to Profitability).pptx
Zepto Case study(On Track to Profitability).pptxZepto Case study(On Track to Profitability).pptx
Zepto Case study(On Track to Profitability).pptx
 
Economic Risk Factor Update: May 2024 [SlideShare]
Economic Risk Factor Update: May 2024 [SlideShare]Economic Risk Factor Update: May 2024 [SlideShare]
Economic Risk Factor Update: May 2024 [SlideShare]
 
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
一比一原版(UCSD毕业证书)加利福尼亚大学圣迭戈分校毕业证成绩单学位证书
 

The Secret Lives of MP3 Files

  • 1. The Secret Lives of MP3 Files Doug Kaye The Conversations Network and GigaVox Media
  • 2. Formats & Encoders • Lossless (WAV, AIFF) • Lossy - MPEG 1, Layer 3 (MP3) - AAC (AAC, M4A, M4B) - MPEG I, Layer 2 (MP2)
  • 3. MPEG Confusion • Lossy Perceptual/Psychoacoustical Codecs • MP3 = MPEG-I Layer 3 • MP2 = MPEG-I Layer 2 (not MPEG-II)
  • 4. Motion Picture Experts Group • MPEG-1:Video CDs, MP3 Audio • MPEG-2: Digital TV, Set-Top Boxes • MPEG-4: Online Multimedia (Video) • MPEG-7: Audio and Video Search • MPEG-21: Multimedia Framework
  • 5. MPEG-1 for Geeks • Layer 1 • Simple 32-Band Algorithm • Philips DCC (Digital Compact Cassette) • Layer 2 (a.k.a. MUSICAM) • Also 32 Bands • International Standard for Broadcasting
  • 6. MPEG-1 Layer 3 (MP3) for Geeks • Psychoacoustic Masking • 32 Bands Divided into 576 Subbands • More Accurate Masking Thresholds • Redundancy Reduction • Lossless Huffman Encoding • Bit-Reservoir Buffering • Joint Stereo
  • 7. Sample Rate for Geeks • The Nyquist Theorem • Sample at 2x the Highest Frequency • 22.05kHz Sample Rate for 11kHz Audio • Sample Rate Is aSource (WAV or AIFF) Property of Uncompressed
  • 8. Sample Rate in Practice • Standardize on 44.1kHz Sample Rate • Flash & Other Players Require n*11.025kHz • Resample if Source is 48kHz from DVDs
  • 9. Bit Rate for Geeks • Independent of Sample Rate • Specifies Encoder Output File Size (CBR) • @64kbps, 1 hour ≈ 27MB • Variable Bit Rate (VBR) • For Higher Bit Rates Only • Not Universally Supported (Avoid It)
  • 10. Bit Rate in Practice • “Use Higher Bit Rates for Music?” • It’s a Myth! • Human Voices Are Complex • Music Masks Its Own Artifacts • 64kbps is Most Common Today • 96kbps is Gaining
  • 11. Podcasting Bit-Rate History • June 2003: 32kbps. “Files too large” • April 2004: 48kbps. “No problem” • September 2004: 64kbps. “Quality is low” • Today: Still 64kbps. • Tomorrow??
  • 12. Stereo Encoding • “Stereo MP3s are twice as large as mono.” • It’s a Myth! • Only Bit Rate Specifies Output File Size • You May Want to Use Higher Bit Rates for Stereo
  • 13. Stereo Encoding for Geeks • Dual Channel or Independent Channel (IC) - Entirely Separate Left and Right • But Most L/R Information is Redundant • Intensity Stereo (IS) • Mid/Side Stereo (MS) • Joint Stereo (JS) Allows IS/MS Combination
  • 14. Stereo Encoding (Even Geekier) • JS Encodes L+R and L-R • If L=R then L-R=0 • SinceUsesRate is ConstantStereo Information Bit L=R Fewer Bits for
  • 15. Stereo Encoding in Practice • StereoReason to (not Music vs.Voice) is a vs. Mono Good Use Higher Bit Rates • Greater Separation Suggests Higher Rates • If Mostly Speech, Consider 100% Mono • If Mono, Make L&R Digitally Identical • Always Encode in Stereo for Compatibility
  • 16. Mastering for MP3 • Help the Encoder: Eliminate Unnecessary Data - High-Pass Filter at 80Hz - Low-Pass Filter at 11kHz (@64kbps encoding) - Normalize
  • 17. Which is Louder? • It’s Not the Height of the Peaks (voltage) • It’s the Area Under the Curve (power)
  • 18. Loudness • What’s the Standard? • We Asked: - Podcasters - Audio Engineers - Radio Engineers • Answer: There Isn’t One • It’s a Hard Problem to Solve
  • 19. Normalization • Peak Normalization (common) - Maximizes Voltage, not Power • RMS Normalization - Maximizes Power (=Loudness) • Determine a Standard Loudness Level
  • 20. Avoid Recording to MP3! • MP3 is a final/release format. • Not designed to be decoded and re-encoded. • Use MP2 Instead... • or the highest MP3 bit rate possible.
  • 21. AAC/M4B Files? • Yes, AAC is Better Than MP3 • We Added AAC to Support iPod Bookmarks • Painful: Only iTunes Could Encode M4B • Doubled Much of Our Workflow • Can’t Be Easily Assembled
  • 22. MP2: Why and When? • MPEG-1 Layer 2 • Designed as an Intermediate Format • The Standard in Broadcast Radio • 128kbps per Track • 44.1kHz Sample Rate Preferred
  • 23. Audio Lessons Learned • MP3 Options • Audio-File Myths • RMS Normalization (Loudness) • AAC/M4B Files (iTunes & iPods) • MP2 Files
  • 24. To Summarize • Record at 44.1kHz Sample Rate (not in MP3!) • Mastering - RMS Normalization (Pick a Standard Level) - 80Hz Hi-Pass, 11kHz Low Pass (for voice) - If Mono, Make L&R Digitally Identical • Encoding - 64kbps when L=R - Consider ≥96kbps for L≠R - Always Use Joint Stereo