Imovie 9 et AVCHD

[jakin1950]

Imacintel Core2 duo 2,4 GH , 3 gigas de Ram . salut j'envisage de donner à mes enfants mon vieux camescope DV à cassette et découvre le numérique actuel
Les camescopes sur carte m'intéressent pour échapper aux pannes de disque dur.
Il me semble qu'imovie 9 décomprime le AVCHD , si c'est le cas, il faut lui donner un disque dur externe et le laisser travailler la nuit , ce n'est pas un plus.

Le renouvellement des modèles est ultrarapide et je m'y perd . Entre 400 et 700 € de budget.
Le sony HDR-SR11E , le Sony HDR-TG3 + housse + Memory Stick Pro 4 Go , le Sony HDR-CX 11 le Sony HDR-CX105 Rouge , sont 'ils reconnus pas imovie ?
j'ai vu aussi le CANON Haute Définition HF100
Est'il utile de filmer en fulll HD pour finir en 950 * 450 pixels sur appleTV?
Votre expérience m'intéresse .
Tant que l'on a pas fait la carte bleue , on peut continuer à réver.
Philippe

Ce message a été modifié par jakin1950 - 9 May 2009, 14:16.

[jakin1950]

merci , tu confirme ce que je supposais
voici la version US :


Join Date: Mar 2007
Location: Eggertsville, NY
Posts: 454

Just to throw in my 2 cents....

Re-rendering as we are discussing it here is the process of taking a file captured in one format (AVCHD) and transforming it into another format (HDV), and, in some cases, converting it back to AVCHD again when a disk is being authored.

The AVCHD compression format is intrinsically lossy and a large amount of data has been literally "thrown away" when the original footage is captured to make the video fit into a comparatively tiny and highly compressed format. Once the footage is converted, or even when it is retained in the same AVCHD format but re-rendered to new and different "groups of pictures", more of the original data is lost.

The compression processes used for video, both mpeg2 and mpeg4, use "motion estimates" to describe how each macroblock differs in comparison to the frames which follow. The only frames which are truly accurate are the I-frames, and all of the intermediary frames (P and are nothing more than a good "guess" as to what the macroblocks will do.

As the new re-compression takes place, artifacts get created, and details get lost in the estimation process.

There is absolutely no way that a file which has been originally captured will retain its original content intact once it has been uncompressed / expanded, then re-compressed. Unlike lossless compression schemes such as used in .zip files like Lempel-Zev, the mpeg video schemes are truly lossy, and the loss is never recoverable.

Can the loss be seen?

It depends on how it is done, how many times it has been applied, what playback devices are used, how critical the viewer is, etc.

Some people look at an iPod and see "perfect quality" video.............

My own strong opinion is that re-compression is visible and undesirable. I try to make all color and white balance adjustments in the camcorder, and smart render (which does NOT do recompression or re-rendering) whenever possible.

The fact that re-rendering takes 8 or 10X real time even on my Intel Extreme 4X3.0 GHz Quadcore is another factor, but I would gladly pay the time panalty if I had a video quality improvement. Such is not the trade-off in this situation however. Re-rendering costs both time and quality.


As tu essayé avec Elgato HD d'utiliser leur programme pour couper les mauvais morceaux des clips . ?