is there any side effect when encoding without audio? (Megui)

[rudolfp]

Hi guys, today i encoded a 1080p mkv video into a smaller size file, i always set the audio track at the beginning but i forgot it by mistake so i started the process without it. Then i wondered how fast the whole encoding process was, it took less time to encode than with audio. There is a significant time save when encoding without audio but is there any negative effect caused by this? (I simply added the forgotten audio track to the video with Meguis "Muxer" function and it seems to be ok) THanks

[LigH.de]

How "significant" is this difference? I would be surprised if it took more than a few minutes to convert the audio of a whole movie with usual playing time (about 2 hours), in relation to the video conversion (probably several hours, depending on the target resolution and other encoder options).

[Bernix]

Hi,
it is I would say advantage! You can do audio in for example LameXP or any specialized audio software with much wider option that usual video encoder software has. Only problem can be muxing it together, usually there is some +/- delay, but this is not problem correct it in Mkvtoolnix, or similar program.

Bernix

[rudolfp]

How "significant" is this difference?

Encoding with audio track added: Start=2:48, End=4:47
Encoding without audio track: Start=5:19, End=5:59

I think this difference is sufficient enough to call it significant.

[Bernix]

It is maybe caused because of audio has HUGE bitrate. And yes, it is significant.
Bernix

[rudolfp]

Yes Bernix, its a 5.1 DTS audio with 1509 kbps. So you say it will be a delay in audio when muxing it together, but how can i find out how many milliseconds it will be?

[Bernix]

Delay or opposite can occur, but not always. The best think to check delay is using VLC and +/- audio. With j and k keys. It is +/- 50ms. Then use in muxer at audiotrack option number you get. In mkvtoolnix is it also as in all others in ms also. And 50ms is hardly noticeable delay. There were discussion about it.
Bernix

[poisondeathray]

How "significant" is this difference?

Encoding with audio track added: Start=2:48, End=4:47
Encoding without audio track: Start=5:19, End=5:59

I think this difference is sufficient enough to call it significant.

Is that encoding audio + video + muxing, vs. encoding audio only ?

Eitherway , there is something wrong with your test numbers. Audio never takes longer to encode than video. Or if you were just "muxing" pre existing audio (steam copy)

Maybe you didn't use equivalent video encoding settings, or maybe you were doing other things like virus scan, or background tasks. It shouldn't take that long to encode audio & mux

Check your log files

[Bernix]

It may needed conversion to wav file, so I think such big file can be difficult to convert. Imagine uncompressed 5.1 DTS for 90 min. size...
Bernix

[rudolfp]

I will specify the whole thing a bit better. The first one (Encoding with audio track added: Start=2:48, End=4:47) shows how long take it Megui to encode a 1080p mkv (14GB) video to a smaller size avi video (1080p mkv with DTS audio to 480p avi with AC3 audio). The encoded file has both video and audio tracks and the whole process takes almost 2 hours (video+audio+muxing). The second one (Encoding without audio track: Start=5:19, End=5:59) shows the same thing but this time i skipped the audio track, so i encoded only the video. This takes only 40 minutes.

I said significant because i can encode a movie without audio and then add the missing audio track later with avidemux or megui and it takes much less time. My only doubt was the delay caused by not encoding with audio but adding/muxing it later to the video or other negative effects. Hope you can understand me and sorry for bad english.

[Bernix]

If supposed wav filesize is about 5 GB, so only reading of file will take in optimal (not ssd) 50 sec. Not talking about writing and recompression. Maybe HDD is bottleneck here.

[gtx780]

Delay or opposite can occur, but not always. The best think to check delay is using VLC and +/- audio. With j and k keys. It is +/- 50ms. Then use in muxer at audiotrack option number you get. In mkvtoolnix is it also as in all others in ms also. And 50ms is hardly noticeable delay. There were discussion about it.
Bernix

How can occur a delay when both video and audio are the same length? For example a a movie with the duration of 1h 24mn 44s, demuxed the audio and then muxed it back together it will stay the same duration so there cant be a delay. Or am i wrong?

[LigH.de]

Having the same duration does not guarantee that both also start with exactly the same timestamp.

[Bernix]

Yes LigH.de is right. It happened to me, when converting separate audio in LameXP to nero aac-HEv2. Muxing video with created audio together in Mkvtoolnix usually I have to set 500 ms, now not clearly remember if positive or negative. It is not to blame lamexp or mkvtoolnix it is normal I think with AAC HEv2 especially.

Bernix

[gtx780]

Yes LigH.de is right. It happened to me, when converting separate audio in LameXP to nero aac-HEv2.

Ok, but he is muxing AVI and AC3 together and not AAC. When i was doing this in the past i had no delay in the resulting encode. If i know it right, Megui shows the delay in milliseconds in the title of encoded audio file.

[Bernix]

O.K. I just mentioned only disadvantage that can occur creating Video and audio separately. I don't think this is related only to High efficiency AAC codec. And encode any audio and lately muxed with video it can happen (I also wrote it c(w)ould not appear. But there is better still to check it after muxing. Therefore is in Mkvtoolnix option for delay and opposite.
And in avi container seems to me bit weaker in sense to correct this.
And last, I think it is advantage to encode audio separately in specialized software like LameXP, because of size and quality, two pass mode and more. I mentioned it in earlier post here that i see this way as advantage. Name of the thread is "is there any side effect when encoding without audio? (Megui)" so probably someone will convert to AAC or any other format and he will not be surprised by delay and easily fix it.

Bernix

[gtx780]

Ok i agree with you Bernix, just why do you think its weak in sense to mux avi+ac3 ? Thanks

[Bernix]

O.k. I think it is not possible avi+ac3 since avi is container (better is xvid+ac3 in avi), but I know what you mean. I think simply AVI is obsolete container, but o.k. for h263, that is right. But when some delay occur how you will fix it? Probably in virtualdub, but not sure if is it possible to shift audio in audio copy mode, probably yes. But still you can keep them in mkv, but I also understand that some DVD players accepts only AVI with xvid, divx (simply h263) codecs inside on USB sticks or DVD medium.
You can keep it in mkv as well with better tracks handling in Mkvtoolnix and other software. That is my opinion.
My english is too poor also explain that "header" of avi file is much bigger (probably much more complicated and therefore not easy manage tracks inside) than mkv or even mp4. Probably someone other explain it better. If I'm not completely wrong again. Overhead is the word. And Overhead can cause delay or not?
Conclusion do not use AVI when you needn't it.
That is my POV
Bernix

[gtx780]

Yes i mean Xvid+AC3 not avi , when some delay occur you can also easily fix it with AVIDemux, you can shift delays in positive or negative values. But its hard to find out if any delay in milliseconds occurs only from watching the video.