Re: [gentoo-user] viewing .m4v files with totem

[Stroller]

Hi Allan,

Glad to have been some help. I can't answer any of your other  
questions, so it might be worth checking out the Totelm mailing list.  
The mplayer developers have a public ftp upload you can use to send  
them problematic files, maybe Totem devs have the same?

Comments continue below...


On 13 Jul 2010, at 21:20, Allan Gottlieb wrote:
> ...
>> You didn't show us what the output (or verbose output) of your ffmpeg
>> command was, so we don't know if the original .m4v had shitty
>> quality,
>> or if you transcoded it.
>
> Here it is with verbose output
>
> ajglap video # ffmpeg -loglevel verbose -i Game_Theory_Lect_20_s.m4v
> Game_Theory_Lect_20_s.avi
> FFmpeg version 0.6, Copyright (c) 2000-2010 the FFmpeg developers
>  built on Jun 21 2010 18:01:44 with gcc 4.4.4
>  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/
> lib64 --mandir=/usr/share/man --enable-static --enable-shared --
> cc=x86_64-pc-linux-gnu-gcc --disable-debug --disable-network --
> enable-libmp3lame --enable-libvorbis --enable-libx264 --enable-
> libxvid --disable-indev=v4l --disable-indev=v4l2 --disable-indev=oss
> --disable-indev=jack --disable-outdev=oss --enable-x11grab --disable-
> vdpau --disable-vdpau --disable-vaapi --disable-altivec --cpu=host --
> enable-gpl --enable-version3 --enable-postproc --enable-avfilter --
> enable-avfilter-lavf --disable-stripping --enable-hardcoded-tables --
> disable-doc
>  libavutil     50.15. 1 / 50.15. 1
>  libavcodec    52.72. 2 / 52.72. 2
>  libavformat   52.64. 2 / 52.64. 2
>  libavdevice   52. 2. 0 / 52. 2. 0
>  libavfilter    1.19. 0 /  1.19. 0
>  libswscale     0.11. 0 /  0.11. 0
>  libpostproc   51. 2. 0 / 51. 2. 0
>
> Seems stream 0 codec frame rate differs from container frame rate:
> 5994.00 (5994/1) -> 29.97 (2997/100)
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Game_Theory_Lect_20_s.m4v':
>  Metadata:
>    major_brand     : M4V
>    minor_version   : 1
>    compatible_brands: M4V M4A mp42isom
>  Duration: 00:33:14.24, start: 0.000000, bitrate: 636 kb/s
>    Stream #0.0(eng): Video: h264, yuv420p, 320x240, 513 kb/s, 29.97
> fps, 29.97 tbr, 2997 tbn, 5994 tbc
>    Stream #0.1(eng): Audio: aac, 44100 Hz, stereo, s16, 118 kb/s
> Output #0, avi, to 'Game_Theory_Lect_20_s.avi':
>  Metadata:
>    ISFT            : Lavf52.64.2
>    Stream #0.0(eng): Video: mpeg4, yuv420p, 320x240, q=2-31, 200 kb/
> s, 29.97 tbn, 29.97 tbc
>    Stream #0.1(eng): Audio: mp2, 44100 Hz, stereo, s16, 64 kb/s
> Stream mapping:
>  Stream #0.0 -> #0.0
>  Stream #0.1 -> #0.1
> Press [q] to stop encoding
> frame=59767 fps=470 q=3.6 Lsize=   67863kB time=1994.23 bitrate=
> 278.8kbits/s
> video:48981kB audio:15580kB global headers:0kB muxing overhead
> 5.113521%
> ajglap video #
>
> ...
> 3.  The conversion from .m4v to .avi costs quality.
>    ffmpeg noted differing frame rates.  Is that relevant?
>    Since the conversion of a 30 minute movie took
>    only a very few minutes, your estimates above suggest that it was
>    just remux-ed and not transcoded, at least not using a demanding
>    codec.

A remux should never affect quality - you're taking the same video  
stream and putting it in another container. The video itself is  
unchanged.

My time estimates were based my use of older Pentium 4 machines - I  
can only guess you have a Core 2 Duo or something? Also, I don't know  
how large this file is? 33 minutes? My "18 - 24 hours" estimate was  
based on a 2 - 3 hour DVD, but also with 2- or 3-pass encoding (which  
you're obviously not performing) and high settings generally. A DVD  
would have higher resolution than your 320x240 clip. Nevertheless, I'm  
a little surprised at how quick your machine is - all my computers are  
so old. :(

The way I read the output above is that ffmpeg determines the input  
file to be 513 kb/s video, and its defaulting to 200 kb/s output - so  
that *is* a transcode. mplayer also states the original to be  513 kb/ 
s, I notice. In fact you would be able to determine the bitrate of  
the .avi file by running the `mplayer -identify` command on it - this  
should confirm that your .avi file is about 200 kb/s, I imagine. That  
confirms transcoding - if you're remuxing the video then the bitrate  
will be lower.

The bitrate is a measure of how much space is consumed on disk to  
store one second of video. So, using the same codec and source  
material, a lower bitrate will tend to be lower quality, as less space  
is consumed storing the details. I think you will probably find  
your .avi to be about 30% - 40% the size of your original .m4v - of  
course it will be lower quality!

That you have determined the original video to be in h264/AAC is good,  
I think. You might try downloading a TED talk, as I think they too use  
these same common codecs. See if Totem plays that.
e.g.: http://www.ted.com/talks/download/video/9151/talk/899

Looking at the wikipedia link I sent you before, I think .m4v is just  
the same as .mp4. I think that if Totem plays an .mp4 TED Talk but not  
your file, then there's a problem with the encoding or format with  
your video.

You might try remuxing your .m4v into .mkv, but I'm not sure what tool  
you'd use. I _think_ you can remux into .avi using `mencoder -copy` -  
I believe an .avi containing h264 and AAC breaks specification, but I  
think most Linux players will tolerate it happily.

I can't immediately think of any other comments to make. Hopefully  
this will give you some more directions to explore.

HTH,

Stroller.