Blocky Video with 544x480 .tivo File

msmart

New member
I've always recorded shows on my S2 TiVo at the Medium setting which produces 480x480 4:3 files. Now with TVS4v600 I started saving them as MP4 files rather than MPEG. I'm using a profile for MP4-IPOD, aspect ratio of 16:9 and output dimensions of 640x358 (letterbox cropping) that has produced many very good files. No complaints.

So I think higher resolution is better so I change the setting on the TiVo to record at Best (544x480). Using the same profile as above produces a file that is very blocky. It looks perfect in the preview window though.

I've only recorded one show this way so I don't know if it's just this one file but because the preview is perfect I'm not sure what to think.

Here is my output profile:

Code:
  <Name>H.264 M4v iPod Touch - 640x358</Name> 
  <OutputMode>Transcode</OutputMode> 
  <FileType>MP4-IPOD</FileType> 
- <OutputLibrary>
  <Program>None</Program> 
  <CustomPath /> 
  </OutputLibrary>
  <DefaultOutputDir /> 
- <VideoAttributes>
  <Encoder>H264</Encoder> 
  <AspectRatio>16:9</AspectRatio> 
  <AspectCorrection>Custom</AspectCorrection> 
- <CropValues>
  <Top>64</Top> 
  <Bottom>58</Bottom> 
  <Left>2</Left> 
  <Right>6</Right> 
  <BackgroundColor>#000000</BackgroundColor> 
  </CropValues>
- <EncodeDimensions>
  <Width>640</Width> 
  <Height>358</Height> 
  </EncodeDimensions>
  <EncodeBitrate>750</EncodeBitrate> 
  <HeaderBitrate>750</HeaderBitrate> 
  <MaxBitrate>1000</MaxBitrate> 
  <ShrinkPercent>100</ShrinkPercent> 
  <EncodingMode>SP</EncodingMode> 
  <UseVBREncoding>True</UseVBREncoding> 
  <DeinterlaceMethod>Smart</DeinterlaceMethod> 
  <MaxGOP>0</MaxGOP> 
  <FrameRate>No Change</FrameRate> 
  <OutputNAVPackets>false</OutputNAVPackets> 
  </VideoAttributes>
- <AudioAttributes>
  <Encoder>AAC</Encoder> 
  <Bitrate>128</Bitrate> 
  <SampleRate>No Change</SampleRate> 
  <AllowMultiAudio>False</AllowMultiAudio> 
  </AudioAttributes>
- <EncodingOptions>
- <H264>
  <profile>baseline</profile> 
  <level_id>30</level_id> 
  <hrd_maintain>true</hrd_maintain> 
  <vbv_size_bytes>750000</vbv_size_bytes> 
  </H264>
  </EncodingOptions>
  </VRDOutputProfile>
I guess I can record at High which is also at 480x480 but a slightly higher bit rate than Medium, but what do I do about this one file then? It's the season finale of Psych.

Ctrl-L output (condensed):

Mux type : TiVo
Video: Encoding : MPEG2
VideoStreamID : xE0
Frame rate : 29.97 fps
Encoding size : 544 x 480
Display dimensions : 544 x 480
Aspect ratio : 4:3
Header bit rate : 5.800 Mbps
VBV buffer : 224 KBytes
Profile : Main@Main
Progressive : Prog or Int
Chroma : 4:2:0
Bit rate : 3.847 Mbps

BTW, I output to 640x358 so the black bars aren't encoded to reduce the file size but up-rez for the iPod Touch (thinking it will look better).

What can be done with this file to get a good MP4 encode? Oh, I also have beta v604 and it produces the same blocky file.
 
Last edited:

Dan203

Senior Developer
Staff member
What do you mean by "blocky"? Does it look pixelated? Or are you talking about motion artifacts?

Also does the file look blocky only when played on the iPod itself? Or does it also look blocky when you play it in a PC based player like QuickTime or VLC?

And what type of iPod are you playing it on?

Dan
 

msmart

New member
Motion artifacts is probably a better way to explain it.

I haven't put it on the iPod yet. I use QuickTime to review the videos before adding them to iTunes.

iPod Touch.
 

Dan203

Senior Developer
Staff member
Have you tried the stock "iPhone / iPod Touch" profile to see if it has the same problem? Try using it and setting your cropping manually via the Options button in the save dialog. Just to see if it makes any difference.

Dan
 

msmart

New member
I hadn't before but did now. Yes, it's better with the stock profile.

So down-rezing 544x480 to 480x256 looks good but uprezing it to 640x358 doesn't. Uprezing 480x480 source to 640x358 has been fine.

To be fair, I guess I should record another show at Best on the TiVo and see how it behaves with my custom profile. I'll do so and post back.
 

Dan203

Senior Developer
Staff member
I think this is mainly just a resolution/bitrate issue. The higher the resolution the less bits that are dedicated to encoding each block of video. The more movement there is in the source the more obvious this deficit is going to be. Another thing that might be helping is the default profile is set to double pass encoding. Your custom profile is single pass. Single pass encodes also exaggerate bitrate deficiencies.

If you want the higher resolution then I think you need to increase the bitrate a little and set it to double pass. That should make the video look better.

Dan
 

msmart

New member
Double pass was it. I changed my profile to double pass and the video looks much better. I also bumped up the bitrate some for added measure.

Case closed. Thanks.
 
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