Audio glitches [video bitrate excedeed]

[Lucius Snow]

Hello all,

I get audio glitches when i read a DVD on some standalones players. The problems occur always at the same moments of the videos while the image is clean by the way (no pixelate or stuff). Strangely, it doesn't happen on every standalone players, neither on a computer. I noticed however that old players are more concerned (> 5 years old). That's the case of my Pioneer DVD-626D.

The audio track is in PCM 48 kHz - 16 bit - Stereo (1536 kbit/s). The video track (encoded by Procoder 2) is PAL - CBR - 7800 kbit/s.

From the tests i made, i concluded that :

- this is not the media because i burnt on genuine Taiyo Yuden TYG03 and other DVD-R medias which are all very reliable

- this is not the authoring software since i tried rendering with DVD architect and DVD lab

- this is not the burning software since i tried burning with DVD architect and Nero

- this is not the total bitrate that would be too high for the players since the video stream is 7800 kbit/s CBR (so both streams audio+video streams are under 9,8 Mbit/s)

Notice also that :

- the problem doesn't occur when there's no video stream muxed with the audio one. By the way, i tried different MPEG2 encoders - and even at lower bitrates - in the case that the video stream would cause problem.

- i couldn't test yet with another DVD burner but i doubt it'd be the guilty (i own a Nec ND-3540).

Of course, when i play the audio source which is a WAVE PCM file on my PC, there's no problem. Then i thought that maybe the checksum, the CRC or something would be guilty, so i transfered the film on a DV tape and captured that one to get back a WAVE PCM file. It was finally identical and that didn't solve the problem.

What do you think about it ? I'm gettings nuts with that. I think i've tried all tracks but there may be another test to do ... ?

Thank you very much.

EDIT : Problem found but still another issue to solve, see below.

[ZippyP.]

Labels on your disks?

[Lucius Snow]

Labels on your disks?

Nope.

[Lucius Snow]

I've spent my whole day to do new tests and i've just found that the problem comes from the video bitrate.

I tried before with lower bitrate but not low enough.

So i encode with Procoder 2.0 : Mastering quality - 7800 kbit/s - CBR. For a DV interlaced source, it gives much better results than CCE or Mainconcept. Here are the full settings :



I downloaded Bitrate viewer (http://www.tecoltd.com ) and here are the results :

Num. of picture read: 78000
Stream type: MPEG-2 MP@ML CBR
Resolution: 720*576
Aspect ratio: 4:3 Generic
Framerate: 25.00
Nom. bitrate: 7800000 Bit/Sec
VBV buffer size: 112
Constrained param. flag: No
Chroma format: 4:2:0
DCT precision: 10
Pic. structure: Frame
Field topfirst: No
DCT type: Frame
Quantscale: Nonlinear
Scan type: ZigZag
Frame type: Interlaced

Average : 7617 kbit/s
Maximum : 8935 kbit/s (that's too much !)

Since my audio track takes 1536 kbit/s, i shouldn't go up than 8000 kbit/s for video since we're close to the 9,8 Mbit/s.

I took two audio glitches and looked what Bitrate viewer indicated at their time. That's 7700 kbit/s and 8200 kbit/s.

I had to set Procoder in VBR (3000 min / 6000 average / 7800 max) to avoid the audio glitches. Some of them disappear but they're still some which keep occuring. Plus, now the quality isn't as good as before with that new bitrate. Since my video takes 52 minutes only, i want the maximum one possible and i think i don't need a VBR. But it seems that Procoder exceeds the set values, especially in CBR. Should i try CQ (constant quality) in Procoder instead ? If yes, with witch settings ? I used CCE before but i let it down for interlaced sources ...

[Lucius Snow]

Okay, new tests done.

6 samples encoded at the sequence when the glitches occur :

Test 1 : CCE SP - CBR 7800 kbit/s
Test 2 : CCE SP - CBR 7500 kbit/s
Test 3 : CCE SP - CBR 7200 kbit/s
Test 4 : CCE SP - CBR 7000 kbit/s

Test 1' : Procoder - CBR 7800 kbit/s
Test 2' : Procoder - CBR 7500 kbit/s
Test 3' : Procoder - CBR 7200 kbit/s
Test 4' : Procoder - CBR 7000 kbit/s

The audio stream is the same used for all videos, a PCM - 48 kHz - 16 bit - Stereo sample.

All of them got the glitch ! It sounded different each time, more or less audible, but there everytime. Bitrate viewer indicated peaks bitrates below 8000 kbit/s for test 3 et 3', and below 7600 kbit/s for test 4 ... So what the hell is going wrong ?

7600 + 1536 = 9136 kbit/s. We're in the norm. And my standalone player is supposed to handle that easily (Pioneer DVD-626D). Same for the others standalone players on which i test.

Well, i'm lost. I want to keep the audio stream in PCM for quality reasons. And i don't want to make a 3000 kbit/s video bitrate to avoid those glitches, especially since my video takes only 52 min, so the DVD can be filled !

What would you recommand ?

Thanks.

[ZippyP.]

What would you recommand ?

High bitrate AC3, 448 kbps. Pretty tough to tell the difference and 1/3 the size of PCM.

[Lucius Snow]

What would you recommand ?

High bitrate AC3, 448 kbps. Pretty tough to tell the difference and 1/3 the size of PCM.

I don't want any lossy compression. Anyway, 448 kbit/s is for 5.1. Since my source is stereo, the bitrate in Dolby digital 2.0 would be 192 kbit/s.

[ZippyP.]

Since my source is stereo, the bitrate in Dolby digital 2.0 would be 192 kbit/s.

Lossy or not, if the bitrate is high enough it is very difficult to tell the difference. 2.0 does not have to be 192, you can go higher than that.