[vdr] Compressing VDR recordings without losing quality.

VDR User user.vdr at gmail.com
Sat Oct 30 03:50:39 CEST 2010


On Fri, Oct 29, 2010 at 10:59 AM, Tony Houghton <h at realh.co.uk> wrote:
>> The only way to not lose quality is to keep the bitrate high,
>> especially for recordings with a lot of motion.  You should encode
>> with constant quality (CRF) set to whatever the minimum quality you
>> want to preserve.  You can also reduce the resolution a bit, just make
>> sure to maintain the aspect ratio.
>
> And don't try to scale interlaced material without using a good
> deinterlacing filter first.

That's a great point, I should have mentioned it but since I didn't,
it's good you did.

>> Bottom line is that you will not
>> get smaller filesizes without making sacrifices.  Data is lost with
>> every encoding pass.
>
> The point of H264 is that it can achieve better quality for a better bit
> rate. Although some quality will be lost by transcoding, you could
> probably halve the file size without making a noticeable difference.

That sounds good when you read the datasheets but real world results
are a bit different.  Also, what you're referring to is encoding
comparisons all from a raw source - not mpeg2 vs. the same mpeg2
reencoded in h264.  I can't stress enough that there is no magic to be
had here for the reasons in my previous post.



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