How-To find Video file Info and What to look for?
From NMTWiki
Easy and suitable for everyone.
Whenever a file has problems with either video or audio or both then the first thing you need to check are the file specs.
There are various applications that can check file specs, including:-
I will use Mediainfo as it covers the widest variety of file formats and is also used elsewhere such as with YAMJ
Contents |
What is MediaInfo?
MediaInfo supplies technical and tag information about a video or audio file. It is free software (free of charge and free access to source code: GPL or LGPL licence)
Mediainfo has downloads for most OS's which can be found via this page. There are commandline aswell as GUI versions with/without installers. The command line version I mention as it is used in YAMJ.
Installing Mediainfo & obtaining file specs
- Install the application and at the end of the install you will be presented with this browser window:-
- Ensure that you select Run after install as then the application will open and present you with the following smaller browser window, if it does not appear then simply run Mediainfo and select Options>Preferences:-
- Make sure you select text output as highlighted. Doing this will allow you to simply copy/paste the output.
- That's it for the install and setup of Mediainfo now off to find the spec of an MKV, Avi or whatever type of file file. The only thing I would add is that if you are looking at a DVD then scan one of the vobs rather than any of the other files types.
- When you find a file you wish to check the specs of then simply right-click on the file and select open with Mediainfo, or Open and then browse to Program Files>Mediainfo and select the mediainfo.exe file.
File spec output
- Here is the output from an MKV file:-
General
Complete name : D:\Movies\movie.mkv
Format : Matroska
File size : 4.37 GiB
Duration : 1h 30mn
Overall bit rate : 6 913 Kbps
Encoded date : UTC 2009-05-30 10:14:46
Writing application : mkvmerge v2.8.0 ('The Tree') built on May 14 2009 09:28:39
Writing library : libebml v0.7.7 + libmatroska v0.8.1
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@ L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 5 frames
Muxing mode : Container profile=Unknown@ 4.1
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 30mn
Bit rate : 5 266 Kbps
Nominal bit rate : 5 403 Kbps
Width : 1 280 pixels
Height : 544 pixels
Display aspect ratio : 2.35
Frame rate : 23.976 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.315
Stream size : 3.33 GiB (76%)
Writing library : x264 core 67 r1145M d2e1e1c
Encoding settings : cabac=1 / ref=5 / deblock=1:-1:-1 / analyse=0x3:0x113 / me=umh / subme=7 / psy_rd=1.0:0.0 /
mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=3 / nr=0
/ decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / keyint=250 / keyint_min=25
/ scenecut=40 / rc=2pass / bitrate=5403 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5
/ ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00
Language : English
Audio
ID : 2
Format : DTS Format/Info : Digital Theater Systems
Codec ID : A_DTS
Duration : 1h 30mn
Bit rate mode : Constant
Bit rate : 1 510 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Surround: L R, LFE
Sampling rate : 48.0 KHz
Resolution : 24 bits
Stream size : 978 MiB (22%)
Language : English
- Now that file only has the one audio track and no subtitles. You have to scroll now to see all of the spec and as well as not being ideal to use it also takes a lot of forum space. Imagine a file with many audio tracks and up to 13 subtitle tracks all listed seperately. Therefore when posting the output on the NMT Forum always use the code tags around the output.
What to look for in the spec?
What to look for in general?
Mediainfo output is split into three sections:-
- General
- Video
- Audio
General:
- Not a lot to see in this Section. Take note of the bitrate though as you'll see how large the difference is between formats. The file above is a 1:1 m2ts and has bitrate of 35mb/s. This does not mean however that your file will always be at or below this bitrate. It may peak at levels above this in VBR files.
- Remember WiFi via USB is only good according to the PopcornHour website for 10mb/s.
Video:
- You can tell the video type from this output. Here it is an AVC with a High profile at Level 5.1.
- This profile allows for bitrates of over 300mb/s and therefore will never be truely fully supported. That does not mean that L5.1 files will not play, that depends on additional factors such as resolution:-
- The file above is a 1080p HD file with a resolution of 1920 x 1080 pixels. The number of pixels then start to decline through 720p and down to SD resolutions. The larger the image the harder the load on the cpu. Generally 720p files will play if they are L5.1 and 1080p L5.1 will play if they have 4 or less reference frames:-
- This file has 11 reference frames. However if you look at the resolution you can see that it is not 1080p so it may play even though it is L5.1 and has 11 reference frames.
Audio:
- Look at the Audio Section to determine the audio type. In the example above it is AC3. Look for AAC and WMA audio if you have no audio. It may be that you require the NMT to decode these types of audio as your Amp may not be able to do so, in which case selecting Analogue PCM should give sound.
- HDMI requires a sampling rate of 32k so if the Sampling rate is less than that and you are using HDMI for your audio you will need to upsample the audio or use other audio connections such as Optical or RCA.
AVI files
If you cannot get an AVI to play or there are problems with the AVI then it can be due to many variables:-
- Encoding application
- File codec
- GMC/QPEL
- Encoding itself
Encoding Applications
To find the encoding application that has been used when you open the AVI with Mediainfo look at the General Section of the output:-
The line Writing Application will tell you the app used to encode. Some apps do not do a very good job at producing AVI files that are hardware compliant. Yes the AVI may play great on a PC with its software players but a hardware player can have issues and either not play the file at all or play out of sync.
Apps giving trouble frequently:-
- Nandub
- Majic
If your AVI has been encoded with one of these apps then you may have to rencode the AVI with VirtualDub/mp3_freeze.
How to deal with a rencode of an AVI file is contained in the NMT Forum guide called How to get none working AVI files to work?
File codec
To find the video codec simply look at the Video section of the Mediainfo output:-
Remember that the NMT is not divx certified. It will play Divx files if they comply to xvid standards.
The example above is an xvid mpeg4 file and should play fine. Look for the details of your file and look for descriptions such as DV, m-jpeg, etc as some camera manufacturers put their own propriatory codec files inside an AVI container.
QMC/QPEL
- Quarter pixel (also known as Q-pel or Qpel) refers to a quarter of a standard pixel. It is used in many modern video encoding standards such as MPEG-4 ASP and H.264/AVC to refer to quarter pixel precision in motion estimation and motion compensation. Though higher precision motion vectors take more bits to encode,
- Videos encoded with quarter-pixel precision motion vectors require up to twice as much processing power to encode, and 30-60% more processing power to decode. As a result, to enable wider hardware compatibility, Qpel is disabled in the default DivX encoding profiles. However, with newer standalone players supporting more complex formats such as VC-1 and H.264, Qpel support in MPEG-4 ASP has become more common.
- Global motion compensation (GMC) is a technique used in video compression to reduce the bitrate required to encode video. It is most commonly used in MPEG-4 ASP, such as with the DivX and Xvid codecs.
- Due to the extra decoding CPU cost of global motion compensation, most hardware players do not support global motion compensation. One example is the Creative Zen Vision M, which supports Xvid and DivX encoded video, but only with GMC disabled.
- DivX has only one GMC "warp point" specified. This enables easier hardware implementation, but limits the global transform to panning operation only. Since panning can be described using blocks, this implementation rarely improves video quality.
- Xvid allows up to 3 warp points, and as a result, has less hardware support. The DivX player, however, does support 3-warp-point GMC, and thus will play GMC Xvid-encoded streams.
- The NMT can cope with 1 warp point but anymore and the video will stall every second or two and the audio won't play. You will have to rencode via the thread over at the NMT Forum.
If you look at the Video section of the Mediainfo output you can see the lines for QPEL/GMC:-
Encoding itself
- There are many parameters that can be tweaked in a video encode. Sometimes by doing this it will push a file out of the spec for a certain profile or container.
- Look for unusual combinations of container/codec. AVI files are space savers over the likes of DVD, so if you get a huge AVI file you can usually bet right that it is a camera video output DV simply slapped in an AVI. This won't work on the NMT and will require encoding with the likes of Windows Movie Maker to get a working avi file.
- VBR or none audio interleaved files may have problems with playback. Again follow the thread and try a remux if there's nothing that strikes you from the Mediainfo output. If that doesn't work look at JUNK removal before finally rencoding.
MKV Files
MKV file issues are covered already in the WIKI on the MKV Troubleshooting page.
- You need to be looking at the way you are playing the file, always test from internal HDD or USB HDD if you have a problem encode.
- Always ensure that you are not taxing the cpu in another way, for example via torrent/usenet downloads. Do not download torrents at the same time as trying to play a 1080p MKV file.
- You then need to consider the Resolution, if it is 720p then it really should play.
- Then look at the video type, is it VC-1? If so support is limited as VC-1 is associated with HD-DVD which is a dead format.
- Look at the profile type, is it High Profile L4, L4.1, L5, L5.1 etc.
- Then look at reference frames as they are key as the larger the resolution of the frames the more cpu power is required. Also the more reference frames the more cpu power. For a rule of thumb 4 or less should be fine.
- Then look at other factors such as the bitrate, type of audio, subtitle streams etc.
All of the information that you require is shown on the Mediainfo output.
The MKV Troubleshooting page has advice on what to do for various issues.
