[FFmpeg-user] Changing DAR ?
Anatol
anatol2002 at gmail.com
Tue Oct 8 11:54:27 CEST 2013
Check:
http://ffmpeg.org/ffmpeg-filters.html#setdar_002c-setsar
On Tue, Oct 8, 2013 at 4:30 AM, Ronald F. Guilmette
<rfg at tristatelogic.com>wrote:
>
> I am trying to use ffmpeg (2.0.1) to make what I believe should be
> a simple change in a video file I have, and it's just not happening,
> so I need to ask what I am doing wrong. (Please note that I am laboring
> under the disadvantage of substantial ignorance about a lot of this stuff,
> so please bear with me and be kind.)
>
> Basically, the file I have, when played on various players, just looks
> wrong, i.e. a big stretched horizontally. I've run mediainfo on the
> file and the output of that is attached below.
>
> I cannot help but notice that in this output, the display aspect ratio
> is set to a rather strange value, i.e. 2.011. I do suspect that the
> proper value should be 16:9 (1.7777). Anyway, I would like to try
> setting it to 16:9 and then see if the video looks reasonably normal
> after that. (I confess that I don't even have any idea as to whether
> that 2.011 value that mediainfo is reporting is relevant to the container
> or to the video stream, so any enlightenment on that point would be
> appreciated too.)
>
> Of course, if I can avoid wholesale re-encoding while ``fixing'' the
> DAR, then I'd like to do that.
>
> So anyway, I've tried ffmpeg (2.0.1) with the "-acodec copy" and
> "-vcodec copy" options and using those, I have run two different
> experiments. In the first, I added "-aspect 16:9" and that had no
> apparent effect at all. In the second I tried instead adding
> -vf setdar=16:9 (although this appears to be a magic undocumented
> thing that, although mentioned in various online posts is most
> definitely _not_ documented in the ffmpeg online documentation at
> all). Anyway, that also had no apparent effect. In both cases,
> running mediainfo on the resulting output files shows the DAR
> _still_ set to the value 2.011, which is not at all what I want.
>
> And help or advice would be appreciated.
>
>
> Regards,
> rfg
>
>
> P.S. I am beginning to think that what the world really needs, in addition
> to a good 5 cent cigar, is a nice tutotial page someplace that would go
> into some depth explaining all of the ins and outs of DAR, PAR, and SAR,
> and which would also clarify not only how to simply _find_ those values
> for any given video (in any given popular format), _both_ as they may be
> encoded in the video stream _and_ also in the container(s), for various
> popular container formats, but also and further, how to _modify_ each of
> those independent aspect ratios, using ffmpeg and other tools, e.g
> WINARChanger, Yamb, etc., again both on the container level and on the
> stream level. After some searching, I have found that this information
> is hard to come by on the web, and when one does find some info on this
> topic, it is fragmentary and almost always unenligntening. (For example,
> I've seen where several people suggest using YAMB to change DAR. OK, so
> I downloaded the thing and installed on omy Win7 system, and managed to
> get it to open the file of interest. Swell. NOW WHAT? If there is a
> way to get this thing to change the DAR I sure as hell don't see it.
> Whatever it is, if it is there, it is non-intutive and non-obvious.
> Sigh. That's OK, I guess. I would prefer to be using ffmpeg from the
> command line over on my FreeBSD system anyway.)
>
> Anyway, maybe I myself might take a stab at writing up a web page like
> what I have suggested just above... the "Video Aspect Ratios for Dummies".
> I would probably be the perfect guy to write this, since I *am* a dummy,
> and so I'd be starting almost from scratch, and (thus) I'd have to
> go 'round and badger all sorts of experts to gather all the info for
> the page, and I would not be polluted by any pre-established under-
> standings of this stuff, since I have (essentially) none.
>
> mediainfo output:
>
> ============================================================================
> General
> Complete name : Kr.avi
> Format : AVI
> Format/Info : Audio Video Interleave
> File size : 105 MiB
> Duration : 5mn 14s
> Overall bit rate : 2 797 Kbps
> Writing library : VirtualDub build 32817/release
>
> Video
> ID : 0
> Format : MPEG-4 Visual
> Format profile : Advanced Simple at L5
> Format settings, BVOP : 1
> Format settings, QPel : No
> Format settings, GMC : No warppoints
> Format settings, Matrix : Default (MPEG)
> Codec ID : XVID
> Codec ID/Hint : XviD
> Duration : 5mn 14s
> Bit rate : 2 593 Kbps
> Width : 720 pixels
> Height : 358 pixels
> Display aspect ratio : 2.011
> Frame rate : 29.970 fps
> Color space : YUV
> Chroma subsampling : 4:2:0
> Bit depth : 8 bits
> Scan type : Progressive
> Compression mode : Lossy
> Bits/(Pixel*Frame) : 0.336
> Stream size : 97.2 MiB (93%)
> Writing library : XviD 64
>
> Audio
> ID : 1
> Format : AC-3
> Format/Info : Audio Coding 3
> Mode extension : CM (complete main)
> Codec ID : 2000
> Duration : 5mn 14s
> Bit rate mode : Constant
> Bit rate : 192 Kbps
> Channel(s) : 2 channels
> Channel positions : Front: L R
> Sampling rate : 48.0 KHz
> Bit depth : 16 bits
> Compression mode : Lossy
> Stream size : 7.20 MiB (7%)
> Alignment : Aligned on interleaves
> Interleave, duration : 33 ms (1.00 video frame)
> Interleave, preload duration : 512 ms
>
>
>
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