Null AC3

[PhillipWyllie]

Is there any way to encode an ac3 file(at say 192kbps) that has no sound(created using avisynth's blankclip), that has singnificantly less file size than an ac3(with sound) of similar length. With testing I havn't been able to achieve this using a variety of encoders(Vegas, Sonic's AC3 encoder). The reason for this as I want to author a DVD with many different titles(residing in the same VTS) that have varying amounts of audio tracks. To keep continuity I need to add the same amout of audio tracks to each title( and repeating audio tracks is space consuming). Thanks

[Krismen]

From: http://www.dvddemystified.com/dvdfaq.html#3.6.2

Dolby Digital is multi-channel digital audio, using lossy AC-3 coding technology from PCM source with a sample rate of 48 kHz at up to 24 bits. The bitrate is 64 kbps to 448 kbps, with 384 or 448 being the normal rate for 5.1 channels and 192 being the typical rate for stereo (with or without surround encoding). (Most Dolby Digital decoders support up to 640 kbps, so non-standard discs with 640 kbps tracks play on many players.) The channel combinations are (front/surround): 1/0, 1+1/0 (dual mono), 2/0, 3/0, 2/1, 3/1, 2/2, and 3/2. The LFE channel is optional with all 8 combinations. For details see ATSC document A/52 <www.atsc.org/document.html>. Dolby Digital is the format used for audio tracks on almost all DVDs.

You can encode mono silence @ 48kHz 64kbps using Aften.

[tebasuna51]

Is there any way to encode an ac3 file(at say 192kbps) that has no sound(created using avisynth's blankclip), that has singnificantly less file size than an ac3(with sound) of similar length.

Nope. Ac3 DVD compatible is always CBR (Constant BitRate) then is not matter if is silence or complex sound, the filesize is always length x bitrate.

[PhillipWyllie]

Thanks for the answers