Is anything being changed or lost by saving a synced ac3 track to FLAC?

(2026-04-22, 04:08 AM)commandrbond Wrote: Is anything being changed or lost by saving a synced ac3 track to FLAC?

Compatibility and space compression. FLAC support is a bit finnicky and might not play on some setups, and since AC3 don't follow a fixed bit depth, transcoding to a safe FLAC 24-bit would be quite notably bigger in file size.

(2026-04-22, 08:17 AM)LucasGodzilla Wrote:

(2026-04-22, 04:08 AM)commandrbond Wrote: Is anything being changed or lost by saving a synced ac3 track to FLAC?

Compatibility and space compression. FLAC support is a bit finnicky and might now play on some setups, and since AC3 don't follow a fixed bit depth, transcoding to a safe FLAC 24-bit would be quite notably bigger in file size.

I ask because I edited an untouched ac3 rip in audacity and exported as FLAC, but when I play them back, the untouched AC3 sounds FAR more dynamic and punchy, even though both waveforms/spectrograms are exactly the same in audacity.  Im guessing it must have something to do with the AC3 metadata being lost in the conversion to FLAC. I even went back and tried reencoding the flac to ac3 using the metadata numbers revealed by Mediainfo to no avail. Still didn't sound right.

(2026-04-22, 06:12 PM)commandrbond Wrote: I ask because I edited an untouched ac3 rip in audacity and exported as FLAC, but when I play them back, the untouched AC3 sounds FAR more dynamic and punchy, even though both waveforms/spectrograms are exactly the same in audacity.  Im guessing it must have something to do with the AC3 metadata being lost in the conversion to FLAC. I even went back and tried reencoding the flac to ac3 using the metadata numbers revealed by Mediainfo to no avail. Still didn't sound right.

AC3 uses Dialnorm that affects gain on playback. Try using eac3to to convert the .ac3 to .wav before editing in Audacity, it should apply Dialnorm when decoding.

I've started using eac3to thanks to this thread and I'm getting the hang of it. However, I ran into an issue this morning on my ld ac3 capture of Jurassic Park. At some point I lost some of the metadata, ie "compr", "dynrng", "mixlevel", and "roomtyp". But it did keep all the other dialnorm settings. My other eac3to film edits all kept that info. I don't think I did anything differently this time. Does that metadata actually make any difference in the end? My preference is to always keep the track as unchanged as possible.

(2026-04-22, 08:46 PM)bronan Wrote:

(2026-04-22, 06:12 PM)commandrbond Wrote: I ask because I edited an untouched ac3 rip in audacity and exported as FLAC, but when I play them back, the untouched AC3 sounds FAR more dynamic and punchy, even though both waveforms/spectrograms are exactly the same in audacity.  Im guessing it must have something to do with the AC3 metadata being lost in the conversion to FLAC.  I even went back and tried reencoding the flac to ac3 using the metadata numbers revealed by Mediainfo to no avail.  Still didn't sound right.

AC3 uses Dialnorm that affects gain on playback. Try using eac3to to convert the .ac3 to .wav before editing in Audacity, it should apply Dialnorm when decoding.

You can also disable DialNorm, and eac3to will apply the correct gain to the audio (so the resulting WAV files sounds much more "louder").

(2026-04-22, 08:17 AM)LucasGodzilla Wrote:

(2026-04-22, 04:08 AM)commandrbond Wrote: Is anything being changed or lost by saving a synced ac3 track to FLAC?

Compatibility and space compression. FLAC support is a bit finnicky and might not play on some setups, and since AC3 don't follow a fixed bit depth, transcoding to a safe FLAC 24-bit would be quite notably bigger in file size.

Not to mention you're gaining very little from doing this, since it's like converting an MP3 file to a 24-bit WAV file.
For editing purposes, it's ok to transcode ac3 to WAV.
But I would encode the final result either back to ac3 or DTS.
Now, decoding DTS-HD MA or TrueHD (16-channel Atmos) tracks to FLAC, makes sense, as you are going from one lossless source to another, BUT you're saving space by encoding one of those tracks to FLAC.
But anything Lossy, it's better to keep it that way.

(2026-04-25, 08:52 PM)emy54 Wrote: Not to mention you're gaining very little from doing this, since it's like converting an MP3 file to a 24-bit WAV file.
For editing purposes, it's ok to transcode ac3 to WAV.
But I would encode the final result either back to ac3 or DTS.
Now, decoding DTS-HD MA or TrueHD (16-channel Atmos) tracks to FLAC, makes sense, as you are going from one lossless source to another, BUT you're saving space by encoding one of those tracks to FLAC.
But anything Lossy, it's better to keep it that way.

Why degrade further with a second lossy encoding? Leave as PCM after editing and all is well.

(2026-04-25, 09:44 PM)bronan Wrote:

(2026-04-25, 08:52 PM)emy54 Wrote: Not to mention you're gaining very little from doing this, since it's like converting an MP3 file to a 24-bit WAV file.
For editing purposes, it's ok to transcode ac3 to WAV.
But I would encode the final result either back to ac3 or DTS.
Now, decoding DTS-HD MA or TrueHD (16-channel Atmos) tracks to FLAC, makes sense, as you are going from one lossless source to another, BUT you're saving space by encoding one of those tracks to FLAC.
But anything Lossy, it's better to keep it that way.

Why degrade further with a second lossy encoding? Leave as PCM after editing and all is well.

I find some players don't really like PCM or FLAC when muxed with video (specially some Android ones).
So when I need to make a copy of a movie to watch on my tablet or VR headset (in case of a 3D movie), I always either encode back to 640kbps DD+ AC3 or DTS.
7.1.4 Atmos tracks that I decode to PCM with MMHelper/Dolby Reference Player combo, on the other hand, gets mixed to Binaural or Ambisonics on Nuendo, as both formats get automatically recognized on Skybox VR or 4XVR, and get the sound delivered properly (as the Atmos mix was meant to be heard, so to speak).
But Atmos is another "rabbit hole". And, unless you worked with any 3D audio format, before, it CAN become quite frustrating to map everything correctly (specially if you don't have an Atmos setup, like I do, and have to do everything through headphones).

But IT IS possible to decode Atmos in its 3D-format and encode it to a 7.1.4 or 9.1.6 WAV/FLAC audio track, nonetheless.

Keep it as FLAC if you can. If a playback device requires another codec and you can't do lossless, 640kbps AC3 is virtually indistinguishable from the master. Even 448 is good for most applications.