Video Editors Step In! FFMPEG / Video Headers Showing Incorrect Information! - GoFuckYourself.com

OnanistsCash · 04-29-2011, 09:01 PM

Quick question, i have a movie, which was cut and rendered with Sony Vegas from its original format to a .wmv file. Here comes the tricky part, movie when played, either with VLC or WMP, has a resolution of 656x480 ... BUT when i run a ffmpeg -i on it, it says it has a resolution of 600x480 ....

I took the time of actually capturing a frame and croping it with photoshop and its 656 and not 600 like ffmpeg its reporting, why would this could be happening? How could i fix the headers resolution? Would that have any impact on video re-rendering? As i said, VLC and WMP seems not to be giving a fuck about the incorrect headers and are playing it right, BUT, jwplayer seems to be using the header information, which i don't blame him, its correct to do that, but why the video headers could be wrong?

ffmpeg -i trailer.wmv

Input #0, asf, from 'trailer.wmv':
Duration: 00:01:04.93, start: 3.000000, bitrate: 2144 kb/s
Stream #0.0: Audio: wmav2, 44100 Hz, mono, 32 kb/s
Stream #0.1: Video: wmv3, yuv420p, 600x480 [PAR 59:54 DAR 295:216], 2065 kb/
s, 25.00 tb(r)

And yeah, the PAR/DAR parameters are also wrong, but honestly, i don't understand that technical shit, usually watch video and make sure it look good, any feedback would be appreciated :P

gir · 04-30-2011, 01:44 PM

ffmpeg tends to break a lot with respect to ratio/fps, usually with propietary formats (WMV) created by broken hw/sw (cameras, windows encoders of questionable quality..)

as you've said, it all comes down to what is specified in the container (RIFF or whatever) and what the actual data (WMV3) tells, it should be the same which it isn't and ffmpeg gets confused.

if you really want to use ffmpeg, the solution is to manually specify -aspect or -fps with ffmpeg and check the result if it plays ok.

finally, jwplayer is probably to blame because it ignores the aspect ratio specified in the flv metadata. you must stretch the video to correct aspect ratio for flv playback, or fix your flv player.

however, when dealing with variety of formats i recommend you vlc/mencoder, which are much more smart about detecting these defects - after all, software dedicated to playback is bound to cope with broken stuff better.

also post questions like that in webmasters Q&A, this section is just too spammy :)

VGeorgie · 04-30-2011, 02:17 PM

Nothing is broken and both are correct. FFmpeg is calculating the stored resolution, and then tells you the ratio between pixel and display aspect ratio is not square (PAR 59:54 DAR 295:216).

For the most part you should avoid encoding to a non-square pixel format in the first place. If your end format is H.264 or Flash a lot of Web-based players will show your video incorrectly, because it has no means to compensate for anamorphic content. You'd be better off going back to Vegas to fix this.

OnanistsCash · 04-30-2011, 03:53 PM

Quote:

Originally Posted by VGeorgie

Nothing is broken and both are correct. FFmpeg is calculating the stored resolution, and then tells you the ratio between pixel and display aspect ratio is not square (PAR 59:54 DAR 295:216).

For the most part you should avoid encoding to a non-square pixel format in the first place. If your end format is H.264 or Flash a lot of Web-based players will show your video incorrectly, because it has no means to compensate for anamorphic content. You'd be better off going back to Vegas to fix this.

Yeah, i thought so, i should re-render video and make sure this time container headers match the frame, the tricky thing here is that i'm sure sure right now which one if the real one, if the one container says of the one VLC detects, i mean, shouldn't Vegas prevent a user from doing that low lever things ( I mean cuting a video footage to X resolution and saving its container information with X resolution? Those are the kind of things low level programs like ffmpeg tend to be used, not the desktop ones .... )

Anyway, right now now even sure if the correct is the one on the container or the one on headers, both look similar .... I guess because it has a high bitrate for the resolution we are talking about and the difference in pixels is not that big .... I guess as you said i will have to go back to Vegas and re-encode everything again

btw bro, you seem to be very into this, how would you check a videos real solution if we consider its container might be wrong? As for example, if i take a still using ffmpeg, it uses the container information to save the still resolution, now if i play it on VLC and capture the screen, it has the other resolution, both look good, how can i detect which is the CORRECT ONE ?

Using my coder mind, i might consider an answer like: "There is no way to know without that information", but you are the pro, is there a way?

gir · 04-30-2011, 05:21 PM

Quote:

Originally Posted by VGeorgie

because it has no means to compensate for anamorphic content.

the means are to stretch the video on stage, according to PAR in the metadata tag to fit the 1:1 DAR of the flash display.
google for "maintain aspect ratio with netstream in as3" if you're curious how to do that.

serious encoders cater for this simply by forcing 1:1 PAR (by stretching the picture before encoding stage) whenever flv output is detected. ffmpeg doesn't do that unless you tell it to (by stating -s resolution, -aspect or -vf setsar=1 with newer ffmpeg)

you're right that having 1:1 PAR since the beggining is probably for the best.

04-29-2011, 09:01 PM	#1
OnanistsCash Confirmed User Industry Role: Join Date: Mar 2011 Posts: 183	Video Editors Step In! FFMPEG / Video Headers Showing Incorrect Information! Quick question, i have a movie, which was cut and rendered with Sony Vegas from its original format to a .wmv file. Here comes the tricky part, movie when played, either with VLC or WMP, has a resolution of 656x480 ... BUT when i run a ffmpeg -i on it, it says it has a resolution of 600x480 .... I took the time of actually capturing a frame and croping it with photoshop and its 656 and not 600 like ffmpeg its reporting, why would this could be happening? How could i fix the headers resolution? Would that have any impact on video re-rendering? As i said, VLC and WMP seems not to be giving a fuck about the incorrect headers and are playing it right, BUT, jwplayer seems to be using the header information, which i don't blame him, its correct to do that, but why the video headers could be wrong? ffmpeg -i trailer.wmv Input #0, asf, from 'trailer.wmv': Duration: 00:01:04.93, start: 3.000000, bitrate: 2144 kb/s Stream #0.0: Audio: wmav2, 44100 Hz, mono, 32 kb/s Stream #0.1: Video: wmv3, yuv420p, 600x480 [PAR 59:54 DAR 295:216], 2065 kb/ s, 25.00 tb(r) And yeah, the PAR/DAR parameters are also wrong, but honestly, i don't understand that technical shit, usually watch video and make sure it look good, any feedback would be appreciated :P __________________ ** GREAT OPPORTUNITY! I SAY IT ;) Selling PaySite + Program + Tons of Promo Content + Hybryd TGP + Everything you need to start quick, jus focus on pushing traffic :P https://gfy.com/showthread.php?t=1071451 GREAT OPPORTUNITY! I SAY IT ;) **

04-30-2011, 01:44 PM	#2
gir Registered User Industry Role: Join Date: Mar 2007 Posts: 13	ffmpeg tends to break a lot with respect to ratio/fps, usually with propietary formats (WMV) created by broken hw/sw (cameras, windows encoders of questionable quality..) as you've said, it all comes down to what is specified in the container (RIFF or whatever) and what the actual data (WMV3) tells, it should be the same which it isn't and ffmpeg gets confused. if you really want to use ffmpeg, the solution is to manually specify -aspect or -fps with ffmpeg and check the result if it plays ok. finally, jwplayer is probably to blame because it ignores the aspect ratio specified in the flv metadata. you must stretch the video to correct aspect ratio for flv playback, or fix your flv player. however, when dealing with variety of formats i recommend you vlc/mencoder, which are much more smart about detecting these defects - after all, software dedicated to playback is bound to cope with broken stuff better. also post questions like that in webmasters Q&A, this section is just too spammy :) Last edited by gir; 04-30-2011 at 01:48 PM..

04-30-2011, 02:17 PM	#3
VGeorgie Confirmed User Join Date: Nov 2008 Posts: 359	Nothing is broken and both are correct. FFmpeg is calculating the stored resolution, and then tells you the ratio between pixel and display aspect ratio is not square (PAR 59:54 DAR 295:216). For the most part you should avoid encoding to a non-square pixel format in the first place. If your end format is H.264 or Flash a lot of Web-based players will show your video incorrectly, because it has no means to compensate for anamorphic content. You'd be better off going back to Vegas to fix this.