Slowdown PAL TS from 25FPS to 24FPS

[Isochroma]

I have a PAL transport stream with AC3 audio that will be converted to AVI (video only) then muxed into MKV with the AC3. It is progressive and doesn't require IVTC or deinterlacing.

I'm aware that film is converted to PAL by increasing the framerate from 24 to 25 FPS, then interlacing. The audio too would be resampled to rate-match the video.

Would it be appropriate to decrease the framerate of the video stream to 24 FPS, and use an audio resampling application such as Audition to slow the audio down by a rate of 24/25?

BTW. the rationale for this process is to restore the original film's time accuracy and audio pitch.

[Inc]

the video ....

mpeg2source("yourTS.d2v")
assumefps(23.976)

and do use besweet or something similair to pitch down (25->23.976) and reencode your source ac3.

[Isochroma]

Thanks for the info! Since it is PAL, and the original film is 24 FPS, I'll use that speed. Mostly I was wondering whether it is correct to do this, rather than how.

Oops, just realized that I'll have to re-encode the audio! Damn, maybe some lossless format that MKV will mux? Does such a thing exist? WAV, maybe.

[MrTroy]

WAV, maybe.
If you're going to do WAV, you can let AviSynth do the framerate conversion. First use AC3toWAV to convert the original ac3 to wav. Then use this avs script:

video=MPEG2Source("Movie.d2v")
audio=WAVSource("Audio.wav")
AudioDub(video,audio)
AssumeFPS(24,sync_audio=true)
SSRC(48000)


As for "whether it's correct to do this": yes. To convert to 25fps the video was sped up, so you can slow it down without problems.

[berrinam]

You don't need to convert to WAV to input into AviSynth; get the NicAudio plugin, then you can directly load AC3s with NicAc3Source. After that, encode the audio in your AviSynth file with BeHappy to FLAC (Free Lossless Audio Codec). That can b e muxed into MKV, and It's going to be more space-efficient than wav.

[Isochroma]

Awesome! You guys have ideas that would have taken me years on my own to learn. I will try these methods...