H264 codec recommendations bitrate/framesize?

[bacardi/avt]

Hi all, I just started to experiment with H264 codec and has been searching for a "guide" to what bitrates usually work good with what framesizes but I can't find any. Can anyone point me in the right direction, please?

And before I get a statment saying: "It depends on what kind of surce you have, high motion or not" I just want to get a general idea and then do my own testing.

[rumplestiltskin]

Sorry, but it depends on the destination. Where do you want to watch the result? iPod? Computer screen (and what size)? TV? TV through iPod?

[bacardi/avt]

mostly on my TV (42" plasma with 720p) and on my computer sometimes (1920x1200 LCD 244T Samsung).

Then some times on my PSP, but I was thinking of the TV in this case. When it comes to the PSP you have other thing limiting your ability to use different framesizes and bitrates.

Lets say I want the same quality as a HDTV rip of a show like Veronica Mars that has been ancoded to Xvid with video bitrate of about 1000kbps and sound in MP3 at 48 kHZ at 128 kbps...what combination would give me the same quality when encoding to MP4 with Video in H264 and sound in AAC?

[jagabo]

Lets say I want the same quality as a HDTV rip of a show like Veronica Mars that has been ancoded to Xvid with video bitrate of about 1000kbps and sound in MP3 at 48 kHZ at 128 kbps...what combination would give me the same quality when encoding to MP4 with Video in H264 and sound in AAC?

Probably about half the Xvid bitrate. But if you don't need files to be an exact size just use single pass constant quantizer (constant quality) mode. Pick the quality (quantizer) you want and encode. Fast, easy, works with any frame size, any frame rate, and any video.

[Soopafresh]

http://gabe.5000megs.com/DeathTheSheepAVCguide.pdf

Good stuff. Easy to read.

[bacardi/avt]

Thanx Soopafresh....that was a very good and easy to understand explanation of the different parameters of the codec.

Exactly what I was looking for.

[edDV]

Xvid and h.264 are both MPeg4.

Figure ballbark is 2-3x more compressed than MPeg2 source for similar quality. Therefore MPeg2 SD @ 6000 Kb/s will compress to 2000-3000Kb/s and 15Kb/s HDTV will compress to 5000-7500 Kb/s.

Forget 1000Kb/s for either if you want quality. Actually the above is an exageration. Those bitrates would assume compression from a master, not a re-compression.

[celtic_druid]

XviD is MPEG-4 Part 2. H.264 is MPEG-4 Part 10.

I really wouldn't recommend encoding via VfW.

[mwbridges]

Lets say I want the same quality as a HDTV rip of a show like Veronica Mars that has been ancoded to Xvid with video bitrate of about 1000kbps and sound in MP3 at 48 kHZ at 128 kbps...what combination would give me the same quality when encoding to MP4 with Video in H264 and sound in AAC?

Probably about half the Xvid bitrate. But if you don't need files to be an exact size just use single pass constant quantizer (constant quality) mode. Pick the quality (quantizer) you want and encode. Fast, easy, works with any frame size, any frame rate, and any video.

Can you give (or point me to) any more details on using quantizer instead of target bit rate? I am looking to convert/ compress from MPEG2 to H.264 with less emphasis on file size (within reason). I am using Nero, which has you set the Mbps as a part of the recoding process.

[rumplestiltskin]

I'll suggest an alternative: MPEG Streamclip. Excellent results, quite configurable. Free.

[jagabo]

Can you give (or point me to) any more details on using quantizer instead of target bit rate? I am looking to convert/ compress from MPEG2 to H.264 with less emphasis on file size (within reason). I am using Nero, which has you set the Mbps as a part of the recoding process.

Unfortunately, Nero Recode doesn't seem to support constant quantizer encoding.

Generally, look for a single pass, constant quantizer (aka target quantizer, constant quality) option. Then all you need to do is select the quantizer or quality value. Most other codec settings (like motion search precision, DCT matrices, etc) work exactly the same as with multipass VBR or CBR encoding.

Basically, what your are doing is telling the codec to make every frame the same visual quality, regardless of what bitrate it takes. Much like with JPEG compression where you can request a quality level and the file turns out to whatever size is required for that quality.

[mwbridges]

I found where Nero allows user to set min and max quantizer when encoding. But, it doesn't appear to ignore thepreviously set Mbps (in previous screen).

If I set these both quantizers to 15, I assume I am getting high-quality constant quality. Correct? This, from what you say, is a better way to ensure a quality relative to the quality of the orginal (i.e. a percentage of the orginal). And, if I use the same quantizer for all encoding, it will ensure consistent quality no matter the size of picture, etc. Is all this correct?

What I don't know is the impact of the set Mbps. It appears to still drive the bit rate in some way.

[jagabo]

That doesn't seem to be quite the same thing as constant quantizer encoding. I reinstalled Nero Express so I could run Recode 2. With a few quick test I found the same thing you did. Even when the min/max quantizers are set to the same value the bitrate setting still has an effect on size of the video.

A true constant quantizer encoding would pay no attention to the bitrate setting. Some encoders do allow you to cap the bitrate to prevent spikes that could cause problems with some players. In this case the encoder would temporarily increase the quantizer during high detail/motion scenes. I wonder if something like this is happening with Nero Recode?

For a true constant quantizer encode you will always get the same quality regardless of the video characteristics. Quality in this sense means how closely the output file matches the input file. Obviously it's not going to turn a badly encoded, low resolution, VHS cap into DVD quality!