Is SheerVideo more accurate than Photo JPEG?
Yes. SheerVideo is a perfect-fidelity codec, while Photo JPEG is a DCT-based approximating codec. For real-world RGB 8b imagery, Apple’s superb Photo JPEG codec at its Best quality setting has an RMS (root mean square) error of 0.70 b/S (bits per sample), whereas SheerVideo has 0.00 b/S error. For Y’CbCr 8bv, whether 4:4:4 or 4:2:2, Photo JPEG’s RMS error is 0.38 b/S, against SheerVideo’s 0.00 b/S error. Despite its lower error rate, SheerVideo compresses 4 times as fast as Photo JPEG and decompresses 3 times as fast as Photo JPEG. Note also that SheerVideo supports alpha compression, which Photo JPEG does not. On the other hand, when quality and speed are less important, Photo JPEG can compress much further than any perfect-fidelity codec.
