hi, currently i am downloading drama series which contain rm, asf, avi and wmv movie file, i would like to know which 1 file format is better quality than other?

.rm is the smallest file size among all 4 mentioned

avi gua.....

Those file format juz a different file compression.....
To see which one got better quality....juz look at the file size....
Big size means good quality....
Usually ppl compress video wif rm or rmvb to save space and this 2 file size is the best compression to compress file wif small size.....

This post has been edited by cyc85: Mar 13 2007, 11:01 AM

.avi better than others,but it will take some space of hdd coz file size

thx to all of u

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Added on March 13, 2007, 11:14 ami have checked my downloaded file, seems that asf file is smaller than others, it only 30-40MB while rmvb file is 130-180MB... does it mean asf file got the poor quality??

This post has been edited by testerretset: Mar 13 2007, 11:14 AM

not really.. some compression software does very good quality... , but technically speaking , AVI(without compressed) is the best quality , u can use K-lite codec's tool - GSpot Codec Information to check whether it's compressed file or not

Many don't get the idea correct. A video+audio file is made up of 3 formats: video compression, audio compression, container. Specifying file extension merely implies the container format, and virtually nothing about quality.
Here is why the topic above doesn't make much sense.
1) For almost all of the video compression format you can find, the quality can be as good as you want, with higher bitrate. When you encode (that is to create the video file), you have a setting to control how good quality or how small file size you want to be. It is pretty obvious that a good video compression format achieve good subjective picture quality at low bitrate (small file size).
To compare between different formats, you start from a high quality video source, using different encoders for each format, adjust the settings until you get very similar subjective quality (it must be slightly degraded compared to source, else you might be setting too high bitrate). Then the smallest file size is the winner. Or in other way, try to get almost same file size, and compare the subjective quality. Currently, the best compression format is MPEG-4 AVC (H.264).

2) Specifying of file extension only tells about container format which has nothing to do with picture quality. It is the video compression that affects quality. Speaking of container formats, the criteria for selection are compatibility, overhead, and video/audio format support. In terms of compatibility, AVI wins because there are quite a lot of hardware players can only work on that. In terms of overhead, Matroska (mkv) and MPEG-4 (mp4) wins. Matroska can clearly produce smaller file than AVI, well the difference might be only 1MB for a 1 hour material. People should slowly move away from AVI because it is old, not fulfilling modern requirements (cannot correctly support those very good video compression eg AVC and audio compression eg AAC), and has high overhead (producing bigger file than necessary).

3) Even with the best compression format AVC, and high bitrate, I can still make it look bad by starting with a bad quality source. In fact, I can make any format look bad. The point here is for a good quality output, one must have a good quality source, then apply modern video compression. Knowledge also plays an important part, some just can't get the deinterlacing, aspect ratio, etc correct.

In short, imagine you are creating the video file from a source, you'll choose video compression format, audio compression format, and container format. You can mix and match the formats. For example:
(video, audio, container), comment
{AVC, AAC, MPEG-4} ;excellent quality-to-bitrate ratio
{MPEG-4 ASP, MP3, MPEG-4}
{MPEG-4 ASP, MP3, AVI} ;common combination
{RealVideo 10, AAC, RealMedia} ;another common combination
{RealVideo 10, AAC, Matroska} ;possible to prove RealMedia has high overhead
{AVC, MP3, Matroska}

The resulting filename only implies the container. Hope you all don't use file extension to specify format.