Most VJs use something very lightly compressed, and use a spatial
only compressor, non temporal codec (some call these editing vs
delivery codecs or intra vs interframe encoding). This makes it
easier to seek to a frame (scratching and jumping around, etc)

More than likely you will be fine with photojpeg (for progressive)
and motion jpeg-b (for interlaced footage) at around 75% quality.

Compressions is a tradeoff with bandwidth and cpu time spent decoding.

For example

Uncompressed 1080i is around 170/sec. Uncompressed Standard Def NTSC
around 27MB/s (not including audio streams)

Compare to HDV and DV which is 3.6MB/sec more here : http:// www.apple.com/xsan/videoworkflow.html

Jpeg codecs live in the middle of that realm, depending on your
quality setting, framesize and frames per second.

If you can sustain the datarates for the number of streams you want
the uncompressed will always win with ease of CPU decoding, at the
expense of being NASTILY hard on your drives.

In other words, Chris was saying, there is no universal answer and
you will have to do some testing.

On Jul 29, 2007, at 11:36 PM, yonsei wrote:

Hi, I see. I am running powerbook G4 1.67 with OS 10.4.10 thank you

Baruch

On Jul 30, 2007, at 2:03 AM, chris clepper wrote:

...

The answer depends a lot on your OS and hardware.

On 7/29/07, yonsei gottlieb@yonsei.ac.kr wrote: Hi,

Is there a 'native' container or codec for [pix_film], in terms of
minimizing cpu load in rendering to gemwin?

I guess qt mov would be the preferred container, but is there
anything better? What about codecs? I have gotten about 33% less
load (than photojpeg) by using uncompressed qt, but is there
anything better?

thanks!

Baruch

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v a d e //

www.vade.info abstrakt.vade.info

hi, some sources suggest that there is no or little advantage to use a
ramdisk in os x because the system caches data which has frequent
access anyway. so a ramdisk can be counterproductive in a cenario where you have
little ram: lets say you have one gig memory. 300 mb are used by some
applications which are open, and another 300 by the system. now you
have a video in your ramdisk of also 300. the system tries to cache
it because it wants to accellerate but can't allocate enough anymore
and data will be swaped on the harddisk.. so you end up with less performance and more harddrive access because
of the ramdisk..

i'm curious about your findings.

greetings, m.

http://lowendmac.com/x-basics/02/0201.html http://www.kernelthread.com/forums/viewtopic.php?t=138

Am 30.07.2007 um 10:08 schrieb Derek Holzer:

vade wrote:

...

If you can sustain the datarates for the number of streams you
want the uncompressed will always win with ease of CPU decoding, at the
expense of being NASTILY hard on your drives.

Chris also suggested using a RAM disk, which would save a lot of wear and tear on the HD in the case of uncompressed video.

I did some research on RAM disks for OS X. Seems like you can skip buying a license for Rambunctious and just use the command line. I promised Baruch that I would post on this, so some recipes follow, copied from various internet sources...

best, d.

---

#!/bin/sh NUMSECTORS=524288 # 64mb = 131072 # 128mb = 262144 # 256mb = 524288 # 512mb = 1048576 # 1gb = 2097152 mydev=hdid -nomount ram://$NUMSECTORS newfs_hfs $mydev mkdir /tmp/ramdrive mount -t hfs $mydev /tmp/ramdrive

Save the file with a name like 'mkramdisk.sh', and give it executable permissions:

chmod 755 mkramdisk.sh

Run it. Voila. This script is right out of the man page for hdid. You can also read about doing this at

http://www.kernelthread.com/mac/osx/arch_fs.html

---

Creating a RAM disk was easy in 9, and, until now, "undocumented"
in X. There is a utility called "ramBunctious" (available at VersionTracker) that brings this functionality back to X (well, at least it puts a GUI on it).

For those of you interested in how this works from the command
line, its pretty simple. First, create a read/write disk image (you can do
this in Disk Copy). Next, create the /dev entry for RAM using the hdid tool. Finally, copy the contents of the disk image to the RAM /dev entry and mount it. Because the disk image is mounted from the /dev entry, any changes occur in RAM. Here are the Terminal commands: [First, calculate the number of 512K blocks you need: numblocks =
(image size in MB) * 2048; for example: 5MB = 10240 blocks]

% hdid -nomount ram://numblocks [result: /dev/disk1]

% dd if=/path/to/image/file.dmg of=/dev/disk1 bs=512 [result:2866+0 records in 2866+0 records out 1467392 bytes transferred in 1 secs (1467392 bytes/sec)]

% hdiutil mount /dev/rdisk1

You need to change the "1" in disk1 and rdisk1 to whatever number is returned by the first command.

Please be sure to check out ramBunctious; it has excellent
documentation on the state of RAM disks in X and when you should/should not use
them.

The reason I mention it here is because it could have a huge positive impact on the functionality of a bootable X cd.

---

How to create a RAM disk on OS X

32768 = size in sectors (16MB in this case, a sector is 512 bytes)

$ hdid -nomount ram://32768 /dev/disk1 $ newfs_hfs /dev/disk1 $ mkdir /tmp/ramdisk1 $ mount -t hfs /dev/disk1 /tmp/ramdisk1

To unmount:

hdiutil detach /dev/disk1

to osx files tiger ramdisk ram disk by peter on Thu Mar 30 16:25:22
EST 2006

---

I have thrown together a quick script for anybody that wants to
create a ramdisk regularly. It's flexible enough for me, but can be edited to offer more options (if u know a little .sh scripting). The disk is dynamicly named and will show up on the desktop when the script is finished. Unmounting can be done as any drive in the finder. The major differences between my and the above approach is that I use
diskutil to mount the created drive, so Finder likes it better, and i give the volume a label, so it can be better recognized by the user ...

Here it is:

Leila:~ samynew[14:30:55]$ cat ramdisk #!/bin/bash if [ -n "$2" ]; then ARG_ERR=ERR; fi if [ -z "$1" ]; then ARG_ERR=ERR; fi if [ -n "$ARG_ERR" ]; then echo 1 argument: size in MB exit fi MB_SIZE=$1 let "MB_SIZE *= 2048" echo Creating ${MB_SIZE} 512-blocks ramdisk CREATED_RAMDISK=hdid -nomount ram://${MB_SIZE} echo New block device: ${CREATED_RAMDISK} DISK_NAME=basename ${CREATED_RAMDISK} echo Creating volume with label: ${DISK_NAME} newfs_hfs -v ${DISK_NAME} /dev/r$CREATED_RAMDISK echo Mounting in /Volumes/${DISK_NAME} mkdir /Volumes/${DISK_NAME} diskutil mount ${CREATED_RAMDISK}

Make sure it's chmodded to be executable: chmod u+x ramdisk Run as: ./ramdisk <size-in-MB>

---

For those of you interested in how this works from the command line, it's pretty simple. First, create a read/write disk image (you can do this in Disk Copy). Next, create the /dev entry for RAM using the hdid tool. Finally, copy the contents of the disk image to the RAM /dev
entry and mount it. Because the disk image is mounted from the /dev
entry, any changes occur in RAM. Here are the Terminal commands:

First, calculate the number of 512K blocks you need: numblocks =
(image size in MB) * 2048; for example: 5MB = 10240 blocks. Open a
terminal and type:

% hdid -nomount ram://numblocks [result: /dev/disk1]

Replace numblocks with the number you calculated in the first step.
Next type:

% dd if=/path/to/image/file.dmg of=/dev/disk1 bs=512 [result:2866+0 records in 2866+0 records out 1467392 bytes transferred in 1 secs (1467392 bytes/sec)] % hdiutil mount /dev/rdisk1

You need to change the "1" in disk1 and rdisk1 to whatever number is returned by the first command.

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Espérance DV Esperance DV is a module for System Preferences making a RamDisk. You can place temporary files for speed saving video, speed recording a
lot of pictures, building your application with xCode,... RamDisk is
the use of a part of read-write memory (RAM) as a hard disk.

http://www.mparrot.net/index.php?page=downloads&lang=en

-- derek holzer ::: http://www.umatic.nl ::: http://blog.myspace.com/ macumbista ---Oblique Strategy # 161: "Trust in the you of now"

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On Mon, 30 Jul 2007, Derek Holzer wrote:

Chris also suggested using a RAM disk, which would save a lot of wear and tear on the HD in the case of uncompressed video.

What's the difference between a file on the HD that can be cached to RAM, and a file on the ramdisk that can be swapped to the HD ? Both can be in either place depending on OS decisions, so...

_ _ __ ___ _____ ________ _____________ _____________________ ... | Mathieu Bouchard - tél:+1.514.383.3801, Montréal QC Canada