44khz to 48khz

[ezekiel999]

Hello again,

I've been converting some tv episodes that I have in AVI format with audio at 44khz to mpeg-2 with 48khz audio so they can be burned to dvd and viewed on a stand alone player.

So far when converting the audio from 44khz to 48khz via DVDLabPro transcode audio program or tmpgenc the audio after converting is out of sync with the video at the end of each 45 minute episode. Each episodes audio starts in sync but by about mid episode its out of sync.

I found out that I could combat this by using GoldWave and timewarping the audio element by a factor basing on using virtualdub-mpeg to figure out the factor. It does work and get back in sync but its pretty time consuming and when I have a lot of episodes to do it takes quite a while.

At any rate I was wondering if there is a audio program (preferrably freeware or shareware) out there that does convert the 44khz audio to 48khz audio and the resulting audio file not suffer from out of sync issues. I was especially curious if anyone else has had a problem similar to mine and found an easier work around solution.

The original audio is wav format and I have been converting it to AC3 because of its much more compressed size but also because I'm under the impression that AC3 audio format is more widely playable on stand alone dvd players versus MPA audio format. Am I wrong about that too?

Thanks for any advice/help offered.

[ungamunga]

I usually use ffmpeg to convert 44kHz wav to 48kHz AC3. Use the following syntax:

ffmpeg -i inputfile.wav -ab X -ar 48000 -ac Y outputfile.ac3

where X is your bitrate (224 is good although I like 384)
where Y is your channals (2 = stereo, 6=5.1 surround; only use 6 if your original wav has 6 channals)

In my experience, this usually fixes most issues with sync (but not all).

If you don't like command lines, use ffmpegGUI or one of the other GUI versions.

[ezekiel999]

Yes I did try that. And that is what I currently use to convert the wav to ac3 but I have to fix the conversion sync issue in the wav after converted from 44khz to 48khz otherwise its out of sync. Over the 45 min episode it gradually gets out of sync and by the end its off by about 45 seconds. Thanks.

[ezekiel999]

One thing I don't understand is why when I convert from the WAV file to AC3 with ffmpeg the audio level is considerably lower. When I'm testing the AC3 in goldwave or what not it seems that the conversion from WAV to AC3 knocked down the audio by some -12db (give or take). The whole reason why I went with AC3 versus WAV was because of how much less disc space the ac3 file takes up. *sigh* When I convert the WAV to MPA or MP2 the audio level is exactly the same as the WAV (good) and same size as the comparable AC3 (good) but the MPA/MP2 format isn't applicable for DVDs on stand alone players, at least not widely supported if I understand it correctly.

Another thing I'm a bit fuzzy about is compressed WAV's? The original source file I was using is MPEG-1 and when I demux it through TMPEnc it comes out into the video component (.m1v) and the audio component (.wav). This wav file is super small 30mb versus the uncompressed wav 600m or even the 192kbps Ac3 conversion which is 60mb. When I click on the properties of the file it shows it as 114kbps, 44khz, mp3 format but its in wav? How is this possible? Is it possible to get it back to this same format after I resample it to 48khz? Is this format suitable for DVD?

Confused but thankful if anyone can follow my mad ravings and make sense of my questions.

[ungamunga]

You get quieter audio with ffmpeg? How peculiar. I find that my AC3 audio volume increases slightly in most cases compared to my wav file. Have you tried using Audacity to tweak the audio volume? I believe that program can be used to increase the recording volume.

MP2 (mpeg-1 layer II) sound is standard for PAL stand-alone players but not NTSC players. Many NTSC players do support MP2 audio, especially players that support VCD playback. However, the NTSC DVD standards only force players to support PCM and AC3 (I think DTS is optional like MP2 is). MP2 playback support is not universal in NTSC land so it is definitely a better idea to encode sound in AC3.

I'm not an expert on it, but does seem that .wav files can be compressed using an MP3 codec. This sort of compressed .wav is the usual output of virtualdub if you use the Save WAV... option when your original AVI had MP3 encoded audio. I've noticed that these compressed .wav files sometimes have wonky durations. However, the .ac3 files created from these .wav files by ffmpeg seem to usually have the correct duration in my experience. I've always assumed that something was a touch wonky in how the codec affects the listed duration for the .wav file. I'm guessing that ffmpeg decodes the audio (thereby getting the correct duration) and then re-encodes it with the correct duration.

[daphy]

One thing I don't understand is why when I convert from the WAV file to AC3 with ffmpeg the audio level is considerably lower. When I'm testing the AC3 in goldwave or what not it seems that the conversion from WAV to AC3 knocked down the audio by some -12db (give or take). The whole reason why I went with AC3 versus WAV was because of how much less disc space the ac3 file takes up. *sigh* When I convert the WAV to MPA or MP2 the audio level is exactly the same as the WAV (good) and same size as the comparable AC3 (good) but the MPA/MP2 format isn't applicable for DVDs on stand alone players, at least not widely supported if I understand it correctly.

very very old bug - use search! stay in MP2, in my opinion changing to AC3 brings no real advantage.

MP2 (mpeg-1 layer II) sound is standard for PAL stand-alone players but not NTSC players. Many NTSC players do support MP2 audio, especially players that support VCD playback. However, the NTSC DVD standards only force players to support PCM and AC3 (I think DTS is optional like MP2 is). MP2 playback support is not universal in NTSC land so it is definitely a better idea to encode sound in AC3.

might be the only aspect

Another thing I'm a bit fuzzy about is compressed WAV's? The original source file I was using is MPEG-1 and when I demux it through TMPEnc it comes out into the video component (.m1v) and the audio component (.wav). This wav file is super small 30mb versus the uncompressed wav 600m or even the 192kbps Ac3 conversion which is 60mb. When I click on the properties of the file it shows it as 114kbps, 44khz, mp3 format but its in wav? How is this possible? Is it possible to get it back to this same format after I resample it to 48khz? Is this format suitable for DVD?

AFAIK ACM compression -> TMPEnc wouldn´t decompress the file at all.

At any rate I was wondering if there is a audio program (preferrably freeware or shareware) out there that does convert the 44khz audio to 48khz audio and the resulting audio file not suffer from out of sync issues. I was especially curious if anyone else has had a problem similar to mine and found an easier work around solution.

there are of course other free options -> besweet (soundtouch function should be interesting and solves your problem) or SSRC, SCRCdrop etc.
take a look on needfulthings you will find some others!
BTW you could also find a nice command reverence for besweet there.

bye Daphy