其實點解唔同 BDP 出來既聲會有明顯分別？

shektau6

還有我有兩部media players，有一部的顔色明顯較另一部淡。兩部都是bitstream output，如果數字影音信號真 ...
Overnite 發表於 2012-1-2 23:50

The source data is the same but different players use different post processing chips unless you choose "source direct" without any post processing.

tinghai

如果大家想了解何謂 Loessless compression 可上 http://www.meridian-audio.com/w_paper/mlp_jap_new.PDF 睇下 Dobly TrueHD 用既 MPL Lossless compression 白皮書. 最重要係呢一句:

“A lossless encoding – decoding system displays an inherent integrity. Once audio has been ‘wrapped up’ in the MLP stream it will remain intact through any intermediate storage or transmission process.”

即係話 compress 咗既data 係未send 去decode之前係唔會有變,就算係bitstream都唔會改裏面既data. 即係話不同BDP player由碟讀出黎直接send出黎既 bit-stream data係一樣亦無所謂post processing. 所有decoding 同processing 係Receiver做. 原理同zip咗D相然後email 俾朋友一樣,所有人unzip出黎既file係一樣,同一部電腦唔同人send個file俾你出黎係一樣,除非係唔同電腦Mon睇先至有分別.

chhanthony

數碼
Bitstream等於digital transfer，
有digital transfer就有jitter，
jitter 多少在於兩部機內clock嘅質數，
唔同jitter會出現音色上嘅不同

模擬
有電流就有失真
唔同嘅諧波失真出現唔同嘅音色

Overnite

如果大家想了解何謂 Loessless compression 可上  睇下 Dobly TrueHD 用既 MPL Lossless compression 白皮 ...
tinghai 發表於 2012-1-3 13:04

Then if the media player does not do any post processing, then why do my two different media players connected to the same AV amp show different video quality? It must be due to the transmission link then.

kc2wong

人地講audio你就講video

回復 24# Overnite

kc2wong

經過streaming的這個過程，就有可能產生誤差。
但我認為個誤差真係不大，兼且睇戲時砰砰澎澎又multichannel情況下，要聽到有分別真係唔容易。
不過貴player個video quaility係會比平機好，都有價值

回復 22# tinghai

tinghai

Then if the media player does not do any post processing, then why do my two different media playe ...
Overnite 發表於 2012-1-3 13:29

Video signal and audio signal are processed separately on the player. There is no bit-stream equivalent of video signal. The player must processed the video data from the disc and convert the MPEG-4 video stream to EIA 861 video standard and sends it over the HDMI cable. The audio data is read and send unprocessed as bit-stream to the receiver for decoding. That is why there is visual difference on the video but there should be no difference in the audio if it is bit-stream and decode by the receiver.

shektau6

如果大家想了解何謂 Loessless compression 可上  睇下 Dobly TrueHD 用既 MPL Lossless compression 白皮 ...
tinghai 發表於 2012-1-3 13:04

   
Yeah, for audio it is the same if bitstream is chosen..the ching above was seeing difference in the picture so i was referring to video content instead...

bbsai

如果大家想了解何謂 Loessless compression 可上  睇下 Dobly TrueHD 用既 MPL Lossless compression 白皮 ...
tinghai 發表於 2012-1-3 13:04

在pdf內, 有項"MLP BITSTREAM FORMATS"
問題出現在這裡,

問題
1) example : Dolby True HD 是包含 Dolby 的數據, 若果 amp. 強行用 Dolby mode, 就可以聽返 Dolby, 即係話Dolby True HD protocol 基建在 Dolby. 咁Dolby True HD 多了甚麼?? 除了個個都知壓縮和data大咗外, 還有甚麼?

2) 每個 player 都有 DRC 功能, 我記得off 咗, 就可以全取整條 bitstream, 令音牆更 wide, 但這功能好似只用於Dolby True HD/dts HD.

3) 當Dolby True HD, 有個sleep mode (Auto/off), off 就可要聽正常條 bitstream.

4) 在 amp. 內, 可以用 Dolby True HD/ Direct surround mode, 為何direct mode 入牆窄??是否無加effect ??

基於4點, 我懷疑Dolby True HD/dts HD 比正常 dolby/dts protocol, 係有機會多咗控制sound effect 的 packet/frame, 我相信ching係讀Electronic Eng. Degree, 你應該明白我講甚麼, 你應該有讀TCPIP protocol, 你應該明白 seven layer, 每一個layer都會後加一些control packet/bit, 更不影響最基本的data. ching 有無Dolby True HD/dts HD 的protocol 圖??  若果有就可以証明是可以外加 sound effect 給廠商, 當製造player時!

還有玩影音讀 Electronic Eng. 的人不止你一個的!!!

Overnite

Video signal and audio signal are processed separately on the player. There is no bit-stream equiv ...
tinghai 發表於 2012-1-3 14:28

Then it is eaiser to explain the differences for video quality due to the processing done in the player.

For audio, I still believe there are differences due to the use of different players and hdmi cables. This is my true experience.

There may be bit error when reading from a blueray disc and when transmitting through an interconnecting cables. When doing file transfer (such as sending a zip file as you said), this is easier to handle as there is no critical timing issue, and therefore we can get 100% copy of the original.

When sending AV signals from one piece of equipment to another, we need to ensure the video and each audio channel (at least six for 5.1) are sent synchronously in a time critical and realtime manner. Once there are errors, with the limited time for error correction, we may have to give up some bits causing degrade of quality.

One may also say that as long as the hdmi cable is guaranteed for a certain bandwidth, then there should be no errors. We may also have to take into account the electromagnetic interference in real-life situation. There are so many signal and power cables behind a typical av system, plus the fast switching circuitries inside each equipment. All these can generate noise to the hdmi cables, which may not have been considered in the testing environment of low end cables. After all, we are talking about transmission of several high speed Gbps streams within the same cable. All these count.

Hope the above can bring some further interactive useful and positive discussion in this subject.