Comparativa objetiva de códecs de audio
Vicente González Ruiz
October 22, 2014
Contents
1 Finalidad
- Aprender a usar el codec Vorbis.
- Aprender a calcular curvas R/D (Rate/Distortion) para lossy audio
codecs.
2 Procedimiento
2.1 Sampling
sudo apt
−get install alsa
−utils
arecord
−f
cd > sample.wav # Push keys CTRL+C to finish sampling
2.2 Encoding
sudo apt
−get install vorbis
−tools
oggenc sample.wav
−o sample.ogg
2.3 Decoding
oggdec sample.ogg
−o sample.wav
2.4 Playing
ogg123 sample.ogg
aplay sample.wav
2.5 Controlling the quality in Vorbis
oggenc
−q
−1 sample.wav
−o sample_m1.ogg # Lowest quality
oggenc
−q 0 sample.wav
−o sample_0.ogg
oggenc
−q 1 sample.wav
−o sample_1.ogg
:
oggenc
−q 10 sample.wav
−o sample_10.ogg # Highest quality
2.6 Encoding with LAME (MP3)
sudo apt
−get install lame
lame
−b 32 sample.wav sample_9.mp3 # Lowest quality
:
lame
−b 320 sample.wav sample_0.mp3 # Highest quality
2.7 The R/D (Rate/Distortion) curve
- Is used for measuring the encoding performance of lossy encoders.
Distortion
^
| * x
| * x
| * x * is better than x
| * x
| * x
| * x
| * x
| * x
+-----------------------> Bit-rate
2.8 Measuring distortion
2.9 Measuring bit-rate
2.10 A Vorbis’s R/D curve
2.11 A MP3’s R/D curve
2.12 Vorbis vs MP3
2.13 Comparación con otros codecs de audio
Modifica los scripts anteriores de forma que sea posible comparar Vorbis y MP3 con
otros codificadores de audio que conozcas.
3 Entregables
Una descripción de los experimentos realizados, sus resultados y unas conclusiones.