Hi, I still do not get proper compression according to the bit rate set. I applied several other changes like playing with the time_base, making sure pts for frames / packets written are “well formed” (i.e. time_base 25000 and frame pts = 0, 1000, 2000, 3000, etc) and other things but have been without luck.
To summarize, here are the generation / conversion pattern for a FullHD video:
1) set bit rate to something invalid (!=0): too strong compression,
effective bitrate 3412 kb/s
2) set bit rate to what I actually want (7257 kb/s): huge result,
effective bitrate 47628 kb/s
3) set bit rate to what I actually want plus rc_min_rate and
rc_max_rate to same value (7257 kb/s): result size / bitrate o.k. but
processing is by a factor of 5 slower than usual…
And here is the reason I mail again… I had a look into the result (ffprobe
-show_frames) from 2) and found no B frames are generated. Instead I see one
‘I’ frame, 11 ‘P’ frames, and repeating this pattern. c->gop_size is set to 12,
anything else I need to set to get B frames (which should reduce the size a
lot)? What possible reasons there are the MPEG4/2 encoder does not generate B
frames?
Greetings Harald
-
Harald Schlangmann
Antwerpener Str. 52, 50672 Köln, Germany
+49 151 2265 4439
[email protected]
www.gps-laptimer.de
On 20.04.2014, at 17:25, Carl Eugen Hoyos <[email protected]> wrote:
> Harald Schlangmann <harry@...> writes:
>
>> Looks I’m doing something fundamentally wrong here.
>
> Did you test with ffmpeg (the application)?
> I am not convinced that single pass encoding can
> generally guarantee a target bitrate.
>
>> Any hint on how to influence result file size for mpeg4?
>
>> The only other fields I initialize for AVCodecContext
>> are width, height, time_base, pix_fmt,
>
> At least constant quantiser vs. bitrate can (and must)
> be set.
>
> Carl Eugen
>
> _______________________________________________
> Libav-user mailing list
> [email protected]
> http://ffmpeg.org/mailman/listinfo/libav-user
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________ Libav-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/libav-user
