Re: Jerky audio playback from local (CD) url
- From: hzgt9b@xxxxxxxxxx <hzgt9bnopostcom@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 23 Oct 2006 13:49:02 -0700
Thanks for your input...
At this point I'll try copying the files to the HD to see if that helps...
"Neil Smith [MVP Digital Media]" wrote:
You will see the same effect on a lot of "enhanced" audio CDs..
What seems to be the same scenario as yours - i.e. an app starts up
which tries to play from one area of the CD, at the same time WMP will
start up and try to autoplay the audio tracks.
Since CD head transport is really very slow indeed, the disk transport
thrashes itself to bits. I've noticed this a lot and always have to
kill the random autoplay exe process to get the thrashing to stop.
I suppose first it's worth checking if WMP is getting autoinsert
notification (you would see it actually playing the media if it's
active when you insert the disk). That could be an outside chance.
Another minor possible is some drives don't "like" CD+R disks or
vice-versa, CD-R disks and don't read them reliably, causing re-reads.
Unfortunately due to the slow head angular velocity, and generally low
transfer rates (4-8MB/s) of CD drives, there's not usually much of a
fix to offer.
If the audio/video is simply one huge clip, it would be worth breaking
it up into chapters using windows media file editor - I haven't looked
at the mess created by Producer for a while
It may well save content as one big single file, and reference a play
point by creating a series of ASX files which specify a StartTime
rather than referencing multiple, manageable media snippets of a few
MB each which could be buffered by the disk electronics and the
player.
Cheers - Neil
On Fri, 20 Oct 2006 11:05:02 -0700, hzgt9b@xxxxxxxxxx
<hzgt9bnopostcom@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Using VS2003, VB.NET,------------------------------------------------
BACKGROUND
I have a window forms based application that will be distributed and
executed directly from CD media. The app contains a TreeView control and a
WebBroswer (AxSHDocVw.AxWebBrowser) control. The TreeView is populated with
nodes that when clicked play an audio clip that is stored on the CD and
navigate the browser control to a specified web URL (also stored on the CD).
Audio playback uses as hidden media player object
(AxWMPLib.AxWindowsMediaPlayer). All the web URLs are html documents that
were converted from individual PPT slides (with animations turned on).
Several (17) of the slides (and subsequent html pages) have an embedded video
object (wmv). The video is played when the video object is clicked 1x.
Because the video was originally embedded in PPT and subsequently converted
to html, the click event that fires the playback of the video is handled
entirely through java script that is created by the PPT to html conversion.
Thus, my app knows nothing about the events in the web pages being loaded
(i.e. my does not interrogate the MSHTML document object during page
navigation/load). The audio clip playback starts after the html page load is
complete (DocumentComplete event handler) - handled directly by my app.
The app is relatively small (~300 kb) but the CD slide content (html, audio
and video clips) is very large (> 500 Mb).
PROBLEM - jerky audio playback on several html pages that have embedded
video objects..
For several of the pages (sequentially, the last 12 slides with video that
are accessed), the audio clip that starts playing after a node is clicked
does not play smoothly. For these slides, it sounds like the CD read head is
moving back and forth on the CD, thrashing around trying to buffer the html's
associated video into memory. My guess is that the CPU is getting tied up
looking for and buffering info from the CD and thus can't stream the audio
clip continuously. For the other slides with video that don't have the audio
problem (sequentially, the 1st 5 slides with video that are accessed), there
is no CD "thrashing" happening - I only hear smooth spinning from the CD (no
stopping and starting, or jerky read head movement).
Multiple CDs of the app and content have been burned from on several
different machines with similar results - jerky audio on these 12 slides.
There seems to be no correlation between the size of the video and/or audio
playback with the jerky playback - the largest audio and video clips
combinations on the CD playback without any jerky behavior.
CAUSE - buffering? CD writer fragmenting video files?
When the CD initially spins up, it spins for quite a while - could it be
that enough info is buffered to playback the 1st 5 videos without having the
read more from the CD?
When the problem occurs I can hear the CD drive stopping and starting and
hear the read/write hear thrashing around - could it be the as the CD is
burned some of the video files are being fragmented over the CD?
Does anyone have any ideas as the to source of the problem, and thusly how
to attack it?
I'm pretty well stumped on this problem - so any feedback would be greatly
appreciated!
Thanks for your attention
-celoftis
Digital Media MVP : 2004-2006
http://mvp.support.microsoft.com/mvpfaqs
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- From: Neil Smith [MVP Digital Media]
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