DivX or MPEG4?

[salem]

I'm trying to encode a batch of movie clips in my computer and play it with TCPMP. Does anyone know which coding is better in quality and size?

Thanks a lot!

[ADBrown]

DivX and MPEG4 are one and the same. All DivX is MPEG4, though not all MPEG4 is DivX.

[isajoo]

DivX and MPEG4 are one and the same. All DivX is MPEG4, though not all MPEG4 is DivX.

:|

come again?

dont get why one is one but the other is not one always.

[ADBrown]

MPEG4 is a general type of video encoding. Particular codecs derived from MPEG4 include Divx, WMV, XviD, Quicktime, 3GPP, and others. So you'll get much the same quality with DivX as with other MPEG4 derivatives.

[GSmith]

MPEG4 is a standard that includes many "parts". The important ones in our case are Parts 2, 3, 10, and 14.

MPEG4 Part 2 is the original MPEG4 video encoding specification that specifies the resultant bitstream itself.
MPEG4 Part 3 is also known as AAC and is an audio successor to MP3.
MPEG4 Part 10 is a newer MPEG4 video encoding specification also known as "AVC" or "H.264".
MPEG4 Part 14 is the file format specification also called, generically, a "container" format.


In general, the confusion between audio encoders, video encoders, and file formats is not readily resolved by the companies that create and promote this software. I've had to learn about all of this through bits and pieces and lots of reading.

The different encoders such as DivX, XviD, 3ivx all can encode into MPEG4 Part 2-compatible bitstreams, yet they encode it using different algorithms thus resulting in various subtle differences in quality. XviD was started by DivX releasing an Open Source version of DivX, called OpenDivX, and now is developed separately. Part of the confusion is that the terms "DivX", "XviD", "3ivx" and others can refer to a company, a program, an encoder, a decoder, an encoding format or a container format. And it is frequently not clear which one is being referred to. This is particularly confusing when referring to one or both of the encoding format and the container format.

In encoders that differentiate between "MPEG4" and "H264" or "MPEG4" and "AVC" as two different ways to encode video, then MPEG4 in this case likely means MPEG4 Part 2 whereas "H264", "H.264", or "AVC" refers to MPEG4 Part 10.

So the reason for the statement that all DivX-encoded video is MP4 is that DivX-encoded video conforms to MPEG4 Part 2. But all MPEG4 video is not DivX: for example, MPEG4 Part 10-encoded video. Incidently, I don't think the first part of this statement is actually true. The latest incarnation of the DivX encoder can, I understand, create ".divx" files which are essentially AVI format enclosing among other things an MPEG4 Part 2 video. And the AVI files would not be MPEG4 Part 14. So calling the result .divx file an "MPEG4" file is misleading at best.

Incidently, Part 10 video is said to be of higher quality than Part 2 for any given file size, but Part 10 is more computationaly expensive. Leading me to surmise that the quality per battery life for Part 10 vs. Part 2 is similar if not slightly favoring Part 2.

I hope this helps! If any of this needs clarifying, please let me know!

Greg Smith
Author, FeederReader - Windows Mobile *direct* RSS news, blogs, audio, video, podcast
www.FeederReader.com - Download on the Road
Author, The Pocket PC Media Chart - www.FeederReader.com/mediachart.html

[salem]

Thanks ADBrown! And Big thanks GSmith the Professor to share this wonderful summarized info about Mpeg-4! It's extremely useful.

I've got another question. If a program is going to encode a video in 'mp4', what program can i use to check the real codec behind it?

In fact, i mainly use Winmenc to encode my videos into DivX format, but it seemed that WinAVI is more user-friendly. The problem is that it only tells me that it's mp4 format, but haven't mentioned what it refers to.

[haesslich]

Salem: Use your media player for your actual PC to check the codec, or use TCPMP to open up the file, then check the Media Info under the File menu - it'll tell you if it's DivX or something else - h.264's a better compression algorithm, but it takes up a LOT more CPU time, which is why Blu-Ray and HD-DVD drives for PC (both of which will be using this instead of the MPEG-2 encoding DVD uses) are going to be.. interesting. As it is, ATI and nVidia are now releasing cards which accelerate h.264 natively, because it really does chew up CPU time (even on an A64, it can take up to 50% of the CPU cycles to decode larger videos using h.264).

But usually if it's in .mp4 format, it's probably DivX or xVID, since that's the file extension Sony's PSP uses natively. I've seen some .mp4 files which used h.264 (AVC) though, so be warned.

[salem]

Salem: Use your media player for your actual PC to check the codec, or use TCPMP to open up the file, then check the Media Info under the File menu - it'll tell you if it's DivX or something else - h.264's a better compression algorithm, but it takes up a LOT more CPU time, which is why Blu-Ray and HD-DVD drives for PC (both of which will be using this instead of the MPEG-2 encoding DVD uses) are going to be.. interesting. As it is, ATI and nVidia are now releasing cards which accelerate h.264 natively, because it really does chew up CPU time (even on an A64, it can take up to 50% of the CPU cycles to decode larger videos using h.264).

But usually if it's in .mp4 format, it's probably DivX or xVID, since that's the file extension Sony's PSP uses natively. I've seen some .mp4 files which used h.264 (AVC) though, so be warned.

Thanks so much Haesslich. I'm going to check it when i'm home tonight. And yes, my .MP4 files mostly come from some ....er.. underground PSP movie sites. :wink:

[gwinter]

GSmith, here's a question I'm hoping you could answer.

The different encoders such as DivX, XviD, 3ivx all can encode into MPEG4 Part 2-compatible bitstreams, yet they encode it using different algorithms thus resulting in various subtle differences in quality.

I read long time ago, that the specification for mp3 (MPEG-1 Layer 3) only details how the decoder should work (and thus what the actual bitstream should look like), leaving the encoder/encoding algorithm open to any kind of design one deemed appropriate. Is this also the case for the MPEG4 Part 2 and the newer Part 10 specification?

[GSmith]

GSmith, here's a question I'm hoping you could answer.

The different encoders such as DivX, XviD, 3ivx all can encode into MPEG4 Part 2-compatible bitstreams, yet they encode it using different algorithms thus resulting in various subtle differences in quality.

I read long time ago, that the specification for mp3 (MPEG-1 Layer 3) only details how the decoder should work (and thus what the actual bitstream should look like), leaving the encoder/encoding algorithm open to any kind of design one deemed appropriate. Is this also the case for the MPEG4 Part 2 and the newer Part 10 specification?

For MPEG4 Part 2, yes, as I tried to imply with my statement "MPEG4 Part 2 is the original MPEG4 video encoding specification that specifies the resultant bitstream itself." For MPEG4 Part 10 I suspect, but I am not sure, that only the resultant bitstream is specified, not the exact encoding algorithm. Note that specifying the bitstream can limit what you can do within the algorithm itself, and of course specifying the bitstream (and its inherent features) gives rise to the overall encoding efficiency and/or quality that can be obtained.

[MTIW Podcast]

I would say go DivX mostly because of its extreme ability to compress large video files yet retain the quality of the original video clips you want to weave together. Bottom line- it will save you space and give you excellent playback.

Cheers!