Hi everybody,

I'm trying to optimize the render profiles for doing screencast.

For starting, i'm trying to optimize a render profil in order to do a 640x480 screencast in mp4.


Based on H.264 600K 2pass's profile, i've modified sound quality and it's quite nice without sensible quality changes (+ ac=1 for mono, ab=128k > 48k, ar=48000>22050):

f=mp4 hq=1 acodec=libfaac ac=1 ab=48k ar=22050 pix_fmt=yuv420p vcodec=libx264 minrate=0 b=600k b_strategy=1 subcmp=2 cmp=2 coder=1 flags=+loop flags2=dct8x8 qmax=51 trellis=1 aspect=%dar s=640x480 pass=2

With a content test it's changing 2 049 001 octets to 1 823 994 octets.

I'have tryied to change other parameters (without understanding all this parameters) as for exemple :

f=mp4 hq=1 me=full me_range=16 subq=5 sc_threshold=40 acodec=libfaac ac=1 ab=48k ar=22050 pix_fmt=yuv420p vcodec=libx264 minrate=0 b=600k b_strategy=1 cmp=+chroma partitions=+parti4x4+partp8x8+partb8x8 coder=1 i_qfactor=0.71 flags=+loop flags2=dct8x8 qmax=51 trellis=1 aspect=%dar pass=2

but it's not better (1 869 146 octets) for the same quality.


Camstasia have a better render that this customized render profil. If it usefull, Camstasia video's information is :

from ffmpeg :

Duration: 00:00:30.20, start: 0.000000, bitrate: 182 kb/s
Stream #0.0(eng): Video: h264, yuv420p, 640x480, 15 tbr, 15 tbn, 30 tbc
Stream #0.1(eng): Audio: aac, 22050 Hz, stereo, s16

from mplayer :

ISO: File Type Major Brand: ISO/IEC 14496-1 (MPEG-4 system) v2
Quicktime/MOV file format detected.
Warning! pts=452000 length=451996
ID_VIDEO_ID=0
[mov] Video stream found, -vid 0
Warning! pts=665600 length=665602
ID_AUDIO_ID=1
[mov] Audio stream found, -aid 1
VIDEO: [avc1] 640x480 24bpp 15.000 fps 0.0 kbps ( 0.0 kbyte/s)
ID_FILENAME=echantillon_mp4/echantillon_mp4.mp4
ID_DEMUXER=mov
ID_VIDEO_FORMAT=avc1
ID_VIDEO_BITRATE=0
ID_VIDEO_WIDTH=640
ID_VIDEO_HEIGHT=480
ID_VIDEO_FPS=15.000
ID_VIDEO_ASPECT=0.0000
ID_AUDIO_FORMAT=mp4a
ID_AUDIO_BITRATE=54728
ID_AUDIO_RATE=22050
ID_AUDIO_NCH=2
ID_LENGTH=30.13
xscreensaver_disable: Could not find XScreenSaver window.
GNOME screensaver disabled
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
Selected video codec: [ffh264] vfm: ffmpeg (FFmpeg H.264)
==========================================================================
ID_VIDEO_CODEC=ffh264
==========================================================================
Forced audio codec: mad
Opening audio decoder: [faad] AAC (MPEG2/4 Advanced Audio Coding)
AUDIO: 44100 Hz, 2 ch, s16le, 54.7 kbit/3.88% (ratio: 6841->176400)
ID_AUDIO_BITRATE=54728
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2
Selected audio codec: [faad] afm: faad (FAAD AAC (MPEG-2/MPEG-4 Audio) decoder)
==========================================================================
AO: [pulse] 44100Hz 2ch s16le (2 bytes per sample)
ID_AUDIO_CODEC=faad
Starting playback...
VDec: vo config request - 640 x 480 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
ID_VIDEO_ASPECT=1.3333
VO: [xv] 640x480 => 640x480 Planar YV12
GNOME screensaver enabled.000 ct: 0.046 76/ 76 9% 0% 1.3% 1 0


Anyone has some ideas to decrease the weight of the output files (without altering the quality) in order to do screencast in mp4 with kdenlive ?

Thanks for your replies :)

Hi. One of the first steps is to create a project profile that has the size of your output and a frame rate of 15fps. Please check our "Creating a video tutorial" section of the
Contribution manual to see a detailled howto:

http://kdenlive.org/contribution-manual/how-make-video-tutorial

That should be a good start to reduce your file size.

Thanks j-b-m for your help :)

I have created one as that... but forgot using it !

So now, effectively, using it, it's as good or better than camstasia ;)

Regards

pepe