Gateway
02-16-2002, 04:40 PM
Ok I have had some time now to spend on the tivo app and been
trying to figure out the audio sync issues.
My tivo settings are BEST with VBR set.
the output from tivo app creates a 544x480 Video file
and i think a 32khz audio file (cant remember) :)
anyhow I pull the show off my tivo using the tivo app
to a tystream, then use tyconvert.
Settings:
output
One Mpeg file
the rest of the settings i dont have anything checked.
this converts the stream into a video file using mpeg2
video/audio altho the audio need to be a differnt bit rate
if your going to vcd or svcd in the end.
now when I pull the stream into dvd2avi and export it
the mpa file is named as the file you save it as
but also adds the delay time for the audio which for my
case the file name was test777MPA-T01-DELAY-196ms.mpa
so some how the app knows that the audio is delayed 196ms
dvd2avi
aspect ratio 4:3
Frame Rate 29.970
Audio Track 192ms delay
so when you take those seperated tracks (video/audio) into
your editing app or other conversion util you will have to
adjust for the audio dely factor. Here is a snipit from at
that explains why audio goes out of sync after time.
-------------------------------------------------------
Because video isn't a perfect 30 frames per second, but
rather 29.97*, syncing audio with a film transfer gets a
ittle more complicated. Now you've got a video version of
the film which is ALMOST real-time, but not quite. The
difference isn't noticable by watching the picture only,
but it presents a problem when trying to syncronize the
sound track to the picture. If you don't slow down the
sound accordingly, you will notice that the sound seems
to drift away from the picture after 30 seconds or so.
The difference in the rates is exactly the same as the
difference between DROP FRAME and NON DROP FRAME video
time code (0.03 frames per second). The drift would
add-up to 18 frames every ten minutes.
** NOTE: If the film was shot at 30 fps, then the audio
must have a x.999 speed adjustment because the film
will be running at 29.97 fps when transferred to video.
So what to do?
*If the field audio carries a 60Hz pilot tone
(which is what most Nagras use to keep the motor
going at a constant speed) you must lock the player
to an external 59.94 Hz crystal to slow it down.
*If the field audio uses time code for sync
(which is how many DATs work) and the time code
on the tape is 30 fps, resolve it to 29.97 to slow it down.
NOTE: Digital field audio can also be speed-altered
by changing the playback rate. (i.e. audio sampled
at 44.1 KHz can be played at 44.056 KHz, or audio
sampled at 48 KHz can be played at 47.952 KHz )
-----------------------------------------------------------
rest of it can be found at:
http://www.zerocut.com/tech/2_3_audio.html
granted they talk about film but its the same theory of
why audio gets out of sync after time.
Now i dont have any issues when i rip from tivo with ty
and convert with ty app with my settings, the audio is
fine, how ever i run into trouble when I want to cut
out commercials if i pull my files into premiere or another
tool and cut out the commercials and re-encode this is where
I run into trouble. So im gonna try adjusting the audio track
in Premiere to reference the 192ms delay cut then re-encode
to what ever format i go to.
anyhow ill give some tests see what I come up with.
Gateway
Pocket-XXX
Porn for your PDA
http://www.pocket-xxx.com
trying to figure out the audio sync issues.
My tivo settings are BEST with VBR set.
the output from tivo app creates a 544x480 Video file
and i think a 32khz audio file (cant remember) :)
anyhow I pull the show off my tivo using the tivo app
to a tystream, then use tyconvert.
Settings:
output
One Mpeg file
the rest of the settings i dont have anything checked.
this converts the stream into a video file using mpeg2
video/audio altho the audio need to be a differnt bit rate
if your going to vcd or svcd in the end.
now when I pull the stream into dvd2avi and export it
the mpa file is named as the file you save it as
but also adds the delay time for the audio which for my
case the file name was test777MPA-T01-DELAY-196ms.mpa
so some how the app knows that the audio is delayed 196ms
dvd2avi
aspect ratio 4:3
Frame Rate 29.970
Audio Track 192ms delay
so when you take those seperated tracks (video/audio) into
your editing app or other conversion util you will have to
adjust for the audio dely factor. Here is a snipit from at
that explains why audio goes out of sync after time.
-------------------------------------------------------
Because video isn't a perfect 30 frames per second, but
rather 29.97*, syncing audio with a film transfer gets a
ittle more complicated. Now you've got a video version of
the film which is ALMOST real-time, but not quite. The
difference isn't noticable by watching the picture only,
but it presents a problem when trying to syncronize the
sound track to the picture. If you don't slow down the
sound accordingly, you will notice that the sound seems
to drift away from the picture after 30 seconds or so.
The difference in the rates is exactly the same as the
difference between DROP FRAME and NON DROP FRAME video
time code (0.03 frames per second). The drift would
add-up to 18 frames every ten minutes.
** NOTE: If the film was shot at 30 fps, then the audio
must have a x.999 speed adjustment because the film
will be running at 29.97 fps when transferred to video.
So what to do?
*If the field audio carries a 60Hz pilot tone
(which is what most Nagras use to keep the motor
going at a constant speed) you must lock the player
to an external 59.94 Hz crystal to slow it down.
*If the field audio uses time code for sync
(which is how many DATs work) and the time code
on the tape is 30 fps, resolve it to 29.97 to slow it down.
NOTE: Digital field audio can also be speed-altered
by changing the playback rate. (i.e. audio sampled
at 44.1 KHz can be played at 44.056 KHz, or audio
sampled at 48 KHz can be played at 47.952 KHz )
-----------------------------------------------------------
rest of it can be found at:
http://www.zerocut.com/tech/2_3_audio.html
granted they talk about film but its the same theory of
why audio gets out of sync after time.
Now i dont have any issues when i rip from tivo with ty
and convert with ty app with my settings, the audio is
fine, how ever i run into trouble when I want to cut
out commercials if i pull my files into premiere or another
tool and cut out the commercials and re-encode this is where
I run into trouble. So im gonna try adjusting the audio track
in Premiere to reference the 192ms delay cut then re-encode
to what ever format i go to.
anyhow ill give some tests see what I come up with.
Gateway
Pocket-XXX
Porn for your PDA
http://www.pocket-xxx.com