Capture music videos and add LPCM-sound

[videoapelsin]

Hi

I'm capturing music videos with my Fire-DTV-T-card, and to get higher quality sound, i'm thinking of adding the audio from wave-files instead of using the broadcastings low-quality mp2-sound.
Of course I have to make sure they've used the same audio-source as released on CD etc.
However, what's the best/easiest program to sync/add the wave-audio with? I want to keep the video as mpeg2 (the dvb-t stream.)

Right now i'm capturing with MyTheatre, Demuxing with PVAStrumento and cutting with Mpeg2Schnitt...

// v

[mimungr]

I don't know about the easiest, but if you're sure both tracks are from the same source, I think the most precise way would be to open both in a graphical audio editor (like Audacity) and line them up with your eyes, rather than your ears.

[CirTap]

ahem.. I'd say "lining up with the ears" is the only way to keep it in true sync, any visual waveformdisplay might support "rough" positioning and aligning, but thats about it.

@videoapelsin: if you have the MPA file (broadcast) AND a matching PCM (CD-rip), load both into whatever audioeditor that supports multiple tracks (Audacity, Soundforge, Wavelab, Cubase <g>)
The MPA will be the "master" for the timing and speed since it came with the video. A CD-rip of the same song may not necessarily play in the exact same speed, even be a slightly different mix ("Radio edit" etc) you may need to cut to match the video version.

If you then move, stretch, squeeze the PCM along to match the MPA you'll hear a phasing sound whenever both tracks are precicely aligned, and as soon as this phasing disappears, you have a drift in the PCM audio.
It's best to have an audio editor which allows large zoom-values so you can move the PCM in very tiny steps, it's usualy just a few microseconds to get the phasing, but they may add up.
Once you have the PCM matching the length and speed of the MPA (~ phasing throughout the song), drop the MPA trck and export the (modified) PCM track to 48kHz so it's DVD compliant.

CirTap

[mimungr]

ahem.. I'd say "lining up with the ears" is the only way to keep it in true sync, any visual waveformdisplay might support "rough" positioning and aligning, but thats about it.

Nonsense. I can sync almost to the individual sample if I do it visually. Try it.

[CirTap]

@mimungr: I know what you're up to, and you can call it nonsene, if you wish, but you won't find an exact match by watching samples only while comparing a MPA and PCM source, and their waveforms -- zoomed to sample-level -- may not even be close, due to the compression or different levels. Seems to me like you have never "seen" a MPA/MP3 and PCM shape of the same recording side by side... your method sounds very academic to me, sorry.
If you notch a track back and force you instantly hear if you're in sync 'cos the mixed audio starts to phase-shift. Period.

If one's not familiar with how sound(s) "look alike", and how to read ind interpret a graphical waveform, those funny spikey images are no help at all. I've done enough (re-)mixes and dubbing over the last two decades, and I've watched several people sitting in front of a waveform trying to align/sync tracks visually and fail, until they started to listen ...

@videoaplesin: find you an audio editor that supports multiple tracks, sound stretching, "time shift", and accurate resampling, play with it, and you're done.

Have fun,
CirTap

[videoapelsin]

hi

Thanks for the answer, I tested with a video earlier today, went fine, no problem. But that music video used the same audio source, guess it'll be more tricky if it's not.

I used Soundforge to resample the PCM to 48kHz, then I used Audacity to get the PCM in sync with the mpa.

Then I used IfoEdit to join the audio and video, then just removed all the files but the *.vob.
Is there a better way to join mpeg2 and pcm?

// v