Audio problems with Virtualdub

[tavaritz]

Hello.

I'm making gameplay videos and now I have the following project to do:

I have two videos (AVIs), recorded by fraps, lets call them A and B. I want to splice B inside A. The way I found that I can do it is crop A in two pieces A1 and A2 cutting it at the point where I want to insert B. Then concatenate them in order A1, B and A2. Works fine except:

When I crop A in the parts A1 and A2 the audio is garbled. In the videos A1 and A2 the audio vibrates about 2Hz.

The settings I use for the cropping is Full processing mode both to Video and Audio, null transform filter and no compression for video or audio. I have LameACM 3.99.5 installed.

What gives?

[jagabo]

It sounds like you are cutting, saving two files, then concatenating those files with a third. Try doing this all in one session:

1) Open A
2) Append B
3) Mark B and Edit -> Cut
4) Position the cursor where you want B inserted and select Edit -> Paste.

[tavaritz]

Thanks.

Worked like charm.

I'm just wondering why does compressing, re-editing and saving deteriorate the video quality. That's why I want to do all my editing in non-compressed version of the video.

[jagabo]

I don't know why the audio was messed up in your original A1 and A2 intermediates.

I'm just wondering why does compressing, re-editing and saving deteriorate the video quality.

Each time you recompress with a lossy codec you will lose quality. That's why they're called lossy. You can use lossless codecs for intermediate files to prevent incremental losses. But those lossless files will usually be very large. And you'll still get a loss at the final encoding.

That's why I want to do all my editing in non-compressed version of the video.

The problem with that is you are limited to cutting on key frames. With long GOP codecs keyframes can be 10 seconds apart or more. Since you are making your own recordings you can specify shorter GOPs for better granularity (but less compression). Or you can use a "smart" editor that only re-encodes cut GOPs.

[tavaritz]

But why does the sound gets garbled when I try to save uncompressed?

This is like being between the rock and the hard place. If I try to save the picture quality between edits I lose my audio quality but if I compress and lose picture quality I retain the audio quality.

There should be a way to save both qualities between edits. Disk space is not the problem.

[davexnet]

But why does the sound gets garbled when I try to save uncompressed?

This is like being between the rock and the hard place. If I try to save the picture quality between edits I lose my audio quality but if I compress and lose picture quality I retain the audio quality.

There should be a way to save both qualities between edits. Disk space is not the problem.

What do you mean by garbled? Is it a momentary glitch at the join point ? Perhaps you can provide a sample showing the problem

[tavaritz]

Sorry but now I'm f***ing confused.

I tried to upload 5s from the begining of the file where one can hear at least 3 times a scratch sound that interrupts the audio. But the file was too big.

So I compressed it to Xvid MPEG-4 and the sound was ok.

The sound is not in any joint point but on the 29 minute original it can be heard about intermittenly but about twice a second eg. 2Hz.

So now I think I just have to live with that if I still can produce a clear sounded texted and compressed version.

[jagabo]

I tried to upload 5s from the begining of the file where one can hear at least 3 times a scratch sound that interrupts the audio. But the file was too big.

So I compressed it to Xvid MPEG-4 and the sound was ok.

I suspect the first 5s clip was uncompressed and there's nothing wrong with the audio. It just that the overall bitrate was too high to play smoothly from your hard drive. So the sound would glitch when the drive was busy fetching more of the video.

[tavaritz]

No.

The original plays well.
The one that has the loading screen part removed and stored uncompressed has audio problems.
And the one I compressed from that to Xvid MPEG-4 has no audio problems.

So solve this.

[jagabo]

That matches what I speculated exactly. Your hard drive is too slow to play uncompressed video and audio smoothly. The bitrate of the uncompressed video is higher than your drive's throughput.

The major hint in your post is that 5s of the video was too big to upload to this site. This site allows up to 500 MB uploads so your 5s file is over 100 MB/s which is around the limit for hard drives (depending on the drive).

[_Al_]

test it exporting uncompressed audio only, to see it is ok,

you'd need to select "Direct Stream Copy" for both video and audio, to not export uncompressed video and audio (you have selected "Full Processing Mode" for both and no compression) , but I have no idea if that editing would still work then

[tavaritz]

That matches what I speculated exactly. Your hard drive is too slow to play uncompressed video and audio smoothly. The bitrate of the uncompressed video is higher than your drive's throughput.

The major hint in your post is that 5s of the video was too big to upload to this site. This site allows up to 500 MB uploads so your 5s file is over 100 MB/s which is around the limit for hard drives (depending on the drive).

Can't be. The original is larger than the uncompressed edited save. If the original plays without any distortion in the audio it cannot be my hard drive speed you idiot.

This is the original:

General
Complete name: C:\SS2 Raw episode 0.avi
Format : AVI
Format/Info : Audio Video Interleave
Format profile : OpenDML
File size : 37.6 GiB
Duration : 29 min 58 s
Overall bit rate : 179 Mb/s

Video
ID : 0
Format : Fraps
Codec ID : FPS1
Duration : 29 min 58 s
Bit rate : 178 Mb/s
Width : 1 280 pixels
Height : 800 pixels
Display aspect ratio : 16:10
Frame rate : 60.000 FPS
Color space : YUV
Bit depth : 8 bits
Bits/(Pixel*Frame) : 2.895
Stream size : 37.2 GiB (99%)

Audio
ID : 1
Format : PCM
Format settings : Little / Signed
Codec ID : 1
Duration : 29 min 58 s
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 329 MiB (1%)
Alignment : Aligned on interleaves
Interleave, duration : 999 ms (59.97 video frames)

And this is the edited:

General
Complete name : D:\DATA\Pictures\Movies\System Shock 2\Work\SS2 Raw episode 0.avi
Format : AVI
Format/Info : Audio Video Interleave
Format profile : OpenDML
File size : 308 GiB
Duration : 29 min 54 s
Overall bit rate : 1 476 Mb/s
Writing library : VirtualDub2 build 42154/release

Video
ID : 0
Format : RGB
Codec ID : 0x00000000
Codec ID/Info : Basic Windows bitmap format. 1, 4 and 8 bpp versions are palettised. 16, 24 and 32bpp contain raw RGB samples
Duration : 29 min 54 s
Bit rate : 1 475 Mb/s
Width : 1 280 pixels
Height : 800 pixels
Display aspect ratio : 16:10
Frame rate : 60.000 FPS
Bit depth : 8 bits
Bits/(Pixel*Frame) : 24.000
Stream size : 308 GiB (100%)

Audio
ID : 1
Format : PCM
Format settings : Little / Signed
Codec ID : 1
Duration : 29 min 54 s
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 329 MiB (0%)
Alignment : Aligned on interleaves
Interleave, duration : 17 ms (1.00 video frame)
Interleave, preload duration : 500 ms

C. and D: are partitions of the same Physical harddrive.

[poisondeathray]

That matches what I speculated exactly. Your hard drive is too slow to play uncompressed video and audio smoothly. The bitrate of the uncompressed video is higher than your drive's throughput.

The major hint in your post is that 5s of the video was too big to upload to this site. This site allows up to 500 MB uploads so your 5s file is over 100 MB/s which is around the limit for hard drives (depending on the drive).

Can't be. The original is larger than the uncompressed edited save. If the original plays without any distortion in the audio it cannot be my hard drive speed you idiot.

This is the original:

General
Complete name: C:\SS2 Raw episode 0.avi
Format : AVI
Format/Info : Audio Video Interleave
Format profile : OpenDML
File size : 37.6 GiB
Duration : 29 min 58 s
Overall bit rate : 179 Mb/s

Video
ID : 0
Format : Fraps
Codec ID : FPS1
Duration : 29 min 58 s
Bit rate : 178 Mb/s
Width : 1 280 pixels
Height : 800 pixels
Display aspect ratio : 16:10
Frame rate : 60.000 FPS
Color space : YUV
Bit depth : 8 bits
Bits/(Pixel*Frame) : 2.895
Stream size : 37.2 GiB (99%)

Audio
ID : 1
Format : PCM
Format settings : Little / Signed
Codec ID : 1
Duration : 29 min 58 s
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 329 MiB (1%)
Alignment : Aligned on interleaves
Interleave, duration : 999 ms (59.97 video frames)

And this is the edited:

General
Complete name : D:\DATA\Pictures\Movies\System Shock 2\Work\SS2 Raw episode 0.avi
Format : AVI
Format/Info : Audio Video Interleave
Format profile : OpenDML
File size : 308 GiB
Duration : 29 min 54 s
Overall bit rate : 1 476 Mb/s
Writing library : VirtualDub2 build 42154/release

Video
ID : 0
Format : RGB
Codec ID : 0x00000000
Codec ID/Info : Basic Windows bitmap format. 1, 4 and 8 bpp versions are palettised. 16, 24 and 32bpp contain raw RGB samples
Duration : 29 min 54 s
Bit rate : 1 475 Mb/s
Width : 1 280 pixels
Height : 800 pixels
Display aspect ratio : 16:10
Frame rate : 60.000 FPS
Bit depth : 8 bits
Bits/(Pixel*Frame) : 24.000
Stream size : 308 GiB (100%)

Audio
ID : 1
Format : PCM
Format settings : Little / Signed
Codec ID : 1
Duration : 29 min 54 s
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 329 MiB (0%)
Alignment : Aligned on interleaves
Interleave, duration : 17 ms (1.00 video frame)
Interleave, preload duration : 500 ms

C. and D: are partitions of the same Physical harddrive.

The bitrate is what matters , not the total size. ie How much data is passed per unit time. When you play a video, you don't transfer the entire file all at once, you play it over time (A media player might only play /decode and buffer a few seconds at any one time). The bitrate is much larger in the edited version because it's uncompressed. Your harddrive is probably too slow - that matches what jagabo was saying

Bit rate : 1 475 Mb/s

1475Mb/s is ~184 megabytes/s . That exceeds most HDD sequential transfer rates for a single HDD (not striped in a Raid-0) . You need a minimum transfer rate sustained of higher than that to not drop frames or stall . The original fraps video bitrate is only 178Mb/s which is only ~22-23 MB/s , well within HDD speed . (Ignoring the overhead for audio and container bitrates for simplicity of discussion)

[sambat]

[QUOTE=poisondeathray;2528499]

That matches what I speculated exactly. Your hard drive is too slow to play uncompressed video and audio smoothly. The bitrate of the uncompressed video is higher than your drive's throughput.

The major hint in your post is that 5s of the video was too big to upload to this site. This site allows up to 500 MB uploads so your 5s file is over 100 MB/s which is around the limit for hard drives (depending on the drive).

Can't be. The original is larger than the uncompressed edited save. If the original plays without any distortion in the audio it cannot be my hard drive speed you idiot.

Calling someone an "idiot" is a term of respect and endearment in Helsinki?

[jagabo]

Can't be. The original is larger than the uncompressed edited save. If the original plays without any distortion in the audio it cannot be my hard drive speed you idiot.

I'm sorry but you are the idiot.

Your source video is 37 GB but the player has 30 minutes to read the data off the drive. So it only requires about 20 MB/s (on average) of transfer rate off the drive.

Your uncompressed video is only 500+ MB but it has to be read off the drive in 5 seconds. So it requires 100+ MB/s of transfer rate.

For the full edited file: it is 308 GB so it needs 171 MB/s throughput to play it in ~30 minutes.

[_Al_]

Calling someone an "idiot" is a term of respect and endearment in Helsinki?

too much vodka, to distinguish what is bigger and what is smaller

[poisondeathray]

BTW, since fraps is I-frame only, you can do the edits with video=> direct stream copy , audio=> direct stream copy, and cut /paste / edit anywhere . Do not use full processing mode. You don't have to recompress

[Bernix]

BTW fraps is obsolete... can anyone tell me any advantage of any payware for screen capture or game capture over OBS studio? Just curious.
Probably I-frame only but i think it is possible to setup OBS in lossless mode and I-frame only too. But why. But there can be some advantages that are hidden to me.


Bernix

[poisondeathray]

BTW fraps is obsolete... can anyone tell me any advantage of any payware for screen capture or game capture over OBS studio? Just curious.
Probably I-frame only but i think it is possible to setup OBS in lossless mode and I-frame only too. But why. But there can be some advantages that are hidden to me.

Yes you can set OBS to record I-frame only too . OBS has more options, more versatile ; I think OBS has option to use GPU encoders too.

But not RGB lossless - that's probably the biggest difference

OBS wasn't available back when fraps was popular. But if you're new or starting now, there are definitely more recording options, and free