Choppy and Sometimes Garbled Audio Playback

[lukelbj]

I have recently noticed that spontaneously VLC will garble and chop up the audio files I am playing (it sounds almost like a CD skipping). The problem started on my laptop (Pentium M 1.7GHz, 512MB RAM, Onboard Graphics, Sound Blaster Audigy 2 NX External USB 24bit soundcard) while I was playing a 16bit/41KHz .wav file. I have been using VLC on my laptop for almost a year now and have 0.8.6b. While I was playing a song for a performance the song started to skip; at first it was hardly noticeable but by the end it was severe. After the performance I replayed the song with VLC but could not reproduce the problem. I even tried loading the computer and plugging another USB device in while in playback but nothing worked. I thought the problem was just a glitch for a while until it started happening on my desktop (Pentium 4 HT 4.0GHz(OC from 3.0GHz), 2GB RAM, ATI Radeon X1600 pro, Realtek ALC889A audio). I recently purchased a new motherboard for my desktop and had to reload windows. After the reload VLC (0.8.6b) worked fine for about a week but then began experiencing the same problems that I saw on my laptop. However, the problem was not a one time thing on my desktop. Every time I played anything with audio VLC would skip and at one point became garbled to the point of silence for several seconds. I tried to set the audio output module to different things but they all skipped somewhat, the worst being Win32 wavOut. I by far experienced the worst problems while using VLC with my TV tuner card: the audio was so bad that the speech on TV could not even be understood. I tried restarting VLC, changing settings, restarting windows but nothing worked. After leaving my computer for about 5 hours and coming back VLC worked fine. I recently downloaded 0.8.6c and installed it to my desktop and so far so good but I am waiting until it begins to give trouble too. Until this is fixed, for my sake, I will not be using VLC for a performance again. An update on my laptop: I noticed the skipping again when using VLC on my laptop with a different file but could not replicate it after the first time. On my laptop it only seems to skip when playing .wav files (then again that is all I play on my laptop, ha!).

I hope this is only a setting I am overlooking or a simple update.
Thanks for reading and hope you can help

[lukelbj]

I can understand why no one has found a solution for my problem because the problem is not being caused by one of VLC's faults, but simply one of it's handy features. VLC by default increases the volume of a played file by almost 50% (just a guess from my tests) I learned and in some cases, when the file being played is at it's maximum without distortion (known as clipping in the amp world) and VLC is increasing it further, the sound card can sometimes experience internal clipping resulting sometimes in skipping and garbled audio. If you have read my previous post this phenomena is easily explained on my desktop. On my laptop, however, the problem was only occasional. I believe I can easily explain this by stating a simple fact: the sound card being used on my laptop was a Sound Blaster Audigy 2 NX, a rather expensive card with quality DACs, and the one being used on my desktop was a Realtek something or another, a cheap card with so-so DACs. The Sound Blaster was able to overcome some of the internal clipping just because it's better made with better parts. But the part that everyone is waiting for is the solution- simple turn the WAV out slider down in your audio control panel until there is no clipping, then your music will be at its maximum volume without distortion.

I was hoping that a well built player like VLC would not be the cause, but some simple setting; I was right.
I will now resume using VLC for my performances as I like the sound quality it offers over my other players.

[WishMaster]

Hey there!

Good call, I've been having the same issues recently. At first I thought I blew my speakers (I've got some Klipsch speakers I like to play LOUD), because all the treble I've been playing through VLC has been crackling. After I decided that they might be blown I noticed that iTunes and WMP were fine. After some forum hunting I found this and dropped the wave out on my SoundBlaster Audigy 2 ZS by 40 - 50 percent and it works like a charm. The funny thing is I don't think it's always been clipping the treble until recently... maybe not I don't know. But thanks again! I'm glad I decided to go forum hunting!

PS Is there a way to lower the volume within VLC so that it doesn't automatically distort audio? I just noticed how it was kinda annoying to not hear my games anymore while listening to music unless I manipulate the volumes for everything. I'll keep playing with some settings until I find a good comfort zone. Hopefully the extra dB is an option somewhere .

[lukelbj]

I think you can turn the default audio volume (Settings-Preferences-Audio) down to around 128 or so and it is the same as reducing it by half. Apparently when using Win32 wave out as your audio output module VLC gets confused between it's own volume and windows wave out volume. To demonstrate this open VLC and play a file, then open you audio control panel and slide the wave out up and down. Watching VLC in the background, you can see its volume meter going up and down as well. Somehow while playing files VLC cranks up the volume even more when using Win32 wave out compared to say DirectX. I don't understand it all but this solution worked with me and hope it does the same with you.

[DJ]

Preferences, Audio "Default audio volume" 256 is 100% in most all other players (50% in VLC). VLC offers 6 db of gain or 512 (100%) in Preferences. A good sound card should be at unity gain when VLC is set at 256 (50%) and the Windows sound volume WAVE slider is full open. Most cards do offer some (but not much) gain in the Master volume control.

BTW 6 db is double the volume. Assuming properly encoded audio (kinda rare these days) unity gain is Representative of FS (full scale) for the converter so that headroom and dynamic range can match the encoded material without clipping. Unfortunately, some formats like AC3 are -8 db below other formats and most users want to boost this. Today many people are transcoding DVDs into other forms without compensating for volume differences in the format, so you can easily end up with a video file with MP3 audio that matches the level of the AC3 original where it should be 8 db louder.