segmenting and then encoding videos for best streaming

[canadianjameson]

Hi,

I'm sort of new to this but I can generally follow a how-to guide

I'm volunteering at a legal research clinic and they just held a symposium at which they recorded the speeches of the presenters. I have the 'raw' .MPG files from the camera, and they just want the different speeches separated (which I think I can do in Avidemux 2.5 which I just downloaded - shame, I have Adobe Premier CS4 on this computer but it seems far more complicated...).

They want to be able to host the files online and let people stream them, but currently there is 25 gigs of files! I figure that there HAS to be a better file format to reduce the size of these.

Can someone either explain what I need to do to get the filesize down (and what the best file size / format for streaming is), or direct me to a very basic tutorial?

Thanks,



Jay

[canadianjameson]

Anyone? I figure this is a quick question to answer...

[JimmyS]

Avidemux should work for you.

Open your MPEG file.
Video and Audio will be set to Copy.
Set Format to MPG-PS (A+V).
Find the start point (frame) of the cut you need. The start frame must be an I type. Use the left and right double-arrow buttons to get to the nearest I frame of the start point. You can verify this with the Frame Type indicator.
Mark the start frame position by clicking red A button.
Find the end point of the cut. I frame type not necessary here.
Mark the end frame position by clicking B button.
File - Save or click the Save button. Don't forget to include the .mpg extension in the name, as it is not put in by default.

Good Luck.

[poisondeathray]

The online format you want for flash is h.264 video, aac audio, in mp4 container. Avidemux can do this for you as well, but it might not put metadata at the beginning (won't play immediately in flash). You might need mp4faststart

[canadianjameson]

Hi Jimmy,

The format option i have for Video are attached (screenshots). The ones you listed specifically were not there. Can you tell me which ones from my lists will work best?

Also, in the mean time I've just been chopping the large video files by speaker using the "A" and "B" buttons (and then saving). It seems to be working so far, so I was a little confused by the Iframe instruction: do i still need to do it?

Thanks so much once again.

Sincerely,



Jay

[poisondeathray]

Are you intending to stream and host these files as is ? Because MPEG2 is not a streaming format. Unless you mean you are uploading to a 3rd party site e.g. vimeo, youtube?

Eitherway the I-frame cutting must be done. Use the "<<" and ">>" buttons at the bottom of the GUI. It will show the frame type as I, P or B

[canadianjameson]

Hi,

Our plan was to host them on our website in an embedded player. We're not too concerned about people being able to download them so flash isn't totally essential.

We did want people to stream as is, so that's why I'm trying to figure out what combination of video and audio codecs / compression will output the smallest file with the best quality (tradeoff)

All frames show as Type I. Does this mean good things?

Thanks,


Jay

[canadianjameson]

also I've been saving all of these as .avi - should I be saving them as mpg? wmv?

[poisondeathray]

I frame is good, this means you can set a in/out point there

best quality/compression was the format I listed earlier. It's a streamable format that you can embed. mpeg, avi - those are NOT formats you can stream and embed

WMV is a format that can stream but requires a different setup, and avidemux cannot export wmv. Quality/compression is a worse than h.264 anyways.


h.264 video, it's called mpeg4-avc in your screenshot
aac audio, it's called AAC(Faac) in your screenshot
mp4 format (container) - not shown in your screenshot

I don't know if avidemux has fixed it yet, but the metadata has to be placed at the beginning of the mp4 file, otherwise it won't play immediately in an embedded player, if you find this is the case use mp4 fast start
http://www.datagoround.com/lab/

cheers

[canadianjameson]

Thanks Poison, that's exactly what I needed!

One more question (before I run off to test, so i might be back).
The format (container) has twp MP4 options:
MP4
and MP4 (PSP)

I assume I choose the non-PSP, right?

Thanks.

p.s: regarding the metadata issue: I will only know if this is a problem once I embed and test, right?
p.p.s: last dumb question: it doesnt give me a file type to save as.... should it be .mp4?

Cheers,



Jay

[poisondeathray]

yes and yes

[canadianjameson]

lol i added one p.p.s but you're too quick and I don't know if you saw it

[canadianjameson]

oh and given that it'll only show up once i embed, should i test that right away or can i save all my files then apply the fix to them all after if need be?

[poisondeathray]

yes, when you save, you have to enter filename.ext

.e.g. "myvideo.mp4" (without the quotes)

oh and given that it'll only show up once i embed, should i test that right away or can i save all my files then apply the fix to them all after if need be?

I would test 1 file first, before you convert a whole bunch only to find out it doesn't work or you don't need to use mp4faststart (they might have fixed it by now, it was an old bug)

Test them locally, and remotely by connecting through external connection

[canadianjameson]

Thanks so much for everything!!!

[SpectateSwamp]

I have shot lots of political forum videos. I use the remote to stop and restart the videos creating many small files. Keeping the videos short is the best. Uploading large files is prone to failure. Youtube allows you to create playlists. It's easier to go right to the mini-video of interest as well. No editing required.

[canadianjameson]

Yea that's what I'm doing. Unfortunately what we had to do was just rent cameras and hit 'record' for 2 hours as a panel of 5-7 people went t the podium one after another so i'm segmenting by speaker. I have to see if we want to use youtube or host on our site

[SpectateSwamp]

Here is my playlist for a Nuclear Discussion forum I videoed.

http://www.youtube.com/my_playlists?p=AFF69E28654CE7B5

Most videos are at or around 2 minutes long. That is the limit that Dropshots.com has for video length. I didn't really care if a word or 2 was lost during the stop/restart of recording. When I was doing local OPEN town council meetings a word or two missing didn't make any difference. I could have skipped it all for that matter. Then they put through resolutions banning camcorders.

Anyway dropshots allows for 20 free videos to be uploaded. Their uploader is 6 to 8 times faster than youtube because it converts to Flash on my computer and sends that file.

So I could upload 20 council video and leave them there for a couple days then reload the next 20 until I had cycled through them all.

If you want to get your video up fast use Dropshots. Surely the cost for more than 20 files won't be that much. With video, getting them up on the net in a hurry is key.

I started using dropshots way back when they were called jusspress.

[canadianjameson]

Hi all,

Sorry to dig this up but now that all is segmented and encoded I've been asked to host these on Vimeo or Youtube and there are issues. The video and audio start out synched but by the end of the video they are out of whack.

Putting aside the notion that the advice given above was faulty, the only thing that I can thing of is that some of these videos were concatenated from 2 segments which were each encoded (as per above) and then appended together. When I did that I got 2 msgs (attached). I hit "no" to both because i have tried all possible combinations and nothing made a difference when playing on my computer.

Can anyone think of any reasons why this is not working?? Why thing would start out smooth and then the audio would lag behind?

A good example is here: http://vimeo.com/27404395

Thanks,



Jay

edit:
Could the audio be the problem? See here: http://vimeo.com/help/compression It says it only supports 44.1khz - is the default setting on the AAC (faac) higher? Is that the issue?

[poisondeathray]

I would use yes to that mode, and yes to rebuild

Did you cut on keyframes ?

Was it out of sync immediately after exporting? or only after youtube or vimeo processed it ? (i.e. when/where was the problem introduced)

Maybe try a different build or Try a nightly build
http://avidemux.org/nightly/win32/

A better idea is to join them before encoding (ie. join the segments as mpeg2 before encoding to avc/aac/mp4)


You can also use other programs to cut e.g. mpg2cut2 , videoredo, then other programs to encode e.g. ripbot, megui, xvid4psp etc...