Having AVCHD Conversion Problem

D

Devilfish

New member
Hi,

I'm new to this site, a friend suggested I try a Hail Mary Pass.

I'm having a persistent problem.

Shooting AVCHD with a Canon Vixia HF S21. Shooting 1920 x 1080, PF30.

I have a dedicated PC for editing using Windows 7 64 bit, SandyBridge K2600 with unlocked Nvidia GPU, Premiere Pro CS5.5 and Adobe fully patched. I import files into Premiere Pro CS5.5 using the automatically detected sequence setting feature to prevent potential import setting conflicts.

I export from PP to Adobe Media Encoder to create an MPEG2. I select the "HDTV 1080p 29.97 High Quality" preset. I change the Multiplexer option to "Variable" bitrate. I change the Video options to "Render at maximum depth" and "VBR, 2 pass" and finally toggle on the "Use Maximum Render Quality" tab. I then export.

Every time I get jerky, buggy playback. If I render the same sequence several times I will always get a jerky playback, but not always in the same spot. I have tried every combination of settings, always with the same result.

If I render the sequence as an H.264, or Microsoft uncompressed AVI the playback is perfect, it's only the MPEG2 that has poor playback.

I purchased a second Canon Vixia HF S21 and it creates files that have the exact same playback problem when converted to an MPEG2.

I readily admit I do not know enough about Premiere Pro. Has anyone else encountered this? Is it a problem with the Canon AVCHD or PF30?

Thank you in advance for any suggestions you may have.
 
Is this playback on your computer, or bluray disk, or what? My first thought is that the problem is with the high-bitrate mpeg2, rather than with the source avchd...
 
Have you tried a different playback program. Like VLC media player, or even see if you have the same probelem in 'Windows Media Center' rather than WMP
 
It seems to me that the disk you're reading the MPEG2 file from is not fast enough. H.264 is compressed and CPU intensive, while MPEG2 is more disk intensive. Having said that, any drive today should be able to play back a single stream. Do you have anything else running in the background? Do you have your video and program files on separate disks?
 
Yes, I have tried playing the MPEG2 back with VLC, same catchy, buggy playback in the same places as WMP. I haven't tried Windows Media Center.

No, nothing else is open when rendering or playing back.

Yes, Premiere Pro is installed on my C drive, while all data is managed on my D drive.
 
Devilfish said:
Yes, I have tried playing the MPEG2 back with VLC, same catchy, buggy playback in the same places as WMP. I haven't tried Windows Media Center.

No, nothing else is open when rendering or playing back.

Yes, Premiere Pro is installed on my C drive, while all data is managed on my D drive.
Click to expand...

What is the bit rate that you achieve with your MPeg2 encoding? For HD, bitrates of 20 Mbits/s seems to be the minimum for 'broadcast' HD. Perhaps some media does better at lower rates, and of course the H.264 codec does better with lower bit rates than MPeg 2.


For playback, there's a combination of CPU to decode, and disk read timing that can affect playback.
 
MPEG2 is an older, less efficient codec than H.264, which is what the original AVCHD is using.

If the H.264 export works fine, use that. It'll give you a better image at comparable bitrates, or the same quality at lesser bitrates.
 
Here is where my knowledge of Media Encoder is limited. I don't know how to determine the bit rate of a rendered MPEG2, I thought it was variable based on the image complexity.

The default settings I'm using in Media Encoder are as follows: "VBR, 2 pass", Minimum bitrate (mbps) "4", Target bitrate (mbps) "15", Maximum bitrate (mbps) "18.5".

GOP settings: M frames 3, N frames 15, Closed GOP every "0", and I toggle on the "Automatic GOP Placement" tab.

Do these settings tell you anything useful? I have never changed them from the default settings that present when MPEG2 is selected as a format.

I prefer to render some sequences to MPEG2 for distribution to others that have older PC's and cannot playback an h.264 format.

Thanks
 
If you drag the mpeg2 file into Premiere, right click it, and select Properties, it will tell you the bit rate (Average Data Rate).

Or..

Just tell me how big the file is on disk and how long it is time-wise.
 
Devilfish said:
Here is where my knowledge of Media Encoder is limited. I don't know how to determine the bit rate of a rendered MPEG2, I thought it was variable based on the image complexity.

The default settings I'm using in Media Encoder are as follows: "VBR, 2 pass", Minimum bitrate (mbps) "4", Target bitrate (mbps) "15", Maximum bitrate (mbps) "18.5".

GOP settings: M frames 3, N frames 15, Closed GOP every "0", and I toggle on the "Automatic GOP Placement" tab.

Do these settings tell you anything useful? I have never changed them from the default settings that present when MPEG2 is selected as a format.

I prefer to render some sequences to MPEG2 for distribution to others that have older PC's and cannot playback an h.264 format.

Thanks
Click to expand...

Waxing philosophical for a moment, if a system is unable to to decode H.264, then it may have problems trying to decode HD Mpeg 2 encoded material... I'd think about lower resolution for such older systems. This is the choice that I usually make for my 'slow' machine... If I want to play 'true' HD, I make a Bluray disk, and play it in my player...

For H.264, 20 Mbits/s is sort of the 'low number' for HD, for 'broadcast' HD, 20 Mbits/s is what is being transmitted as a 'max'. Since Mpeg 2 is less efficient, it would seem one would select a higher bit rate to 'match' quality of H.264. Since I don't usually encode to Mpeg 2... I'm sort of using this reasoning. This has the somewhat negative effect of requiring a higher performance CPU to process it...

As for the GOP parameters, I usually take the defaults as they are.

While this probably has as many holes as swiss cheese... if SD media can be compressed into a 8 Mbits/s stream with Mpeg 2, then it would require 4x for the HD, or 32 Mbits/s... Of course one can encode SD into a 'clean' 6 Mbits/ so that would be 24 Mbits/s. Codec compression may not scale as spatial resolution increases... but it may be a 'start' estimate.

One can get under 6 Mbits with SD material, but then quality suffers, or one drops to a 15 fps rate, or something like that to get 1-3 Mbits/s.
 
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