ENC-400-HDMI
™ H.264 Encoder
User Guide V 2.1
19
3.4.2
Menu: Encoder / Video
shows the ‘Encoder / Video’ page of the ENC-300™ encoder and Table 7 describes it.
Figure 10: Encoder / Video' page of the ENC-
300™ encoder
Settings:
Description:
Codec:
Displays the video codec of the output stream. (Read only)
Bitrate:
Specifies the video bitrate in kBit/s of the output stream.
Intra Frame Interval: Specifies the interval of intra frames. Intra frames (= I-Frames) are total
independently coded and are used as references frames.
Additional Information about P-Frames and GOP length:
At the ENC-
300™ the data volume of a P-Frame amounts between 5% and 20%
of an I-Frame. If is assumed of an average data volume of 10%, it means that
for one I-Frame or ten P-Frames the same data volume is needed. The H.264
standard allows long GOPs. The ENC-
300™ limits the GOP length to 500
frames. More P-Frames at the same data rate means also a better quality. But
more P-Frames have also two disadvantages: 1) The decoder can start the
decoding process not till then the decoder get an I-Frame. That means at a GOP
of 500 frames, the decoder waits in worst case 20 seconds before a picture can
be displayed. 2) The result of this is also, that at occurrence of network errors
(high packet loss), Frame gaps of up to 20 seconds can occur. So, the lower the
P-Frames, the higher are the robustness and the faster can be switched the
streams.
VBV Size [ms]:
Specifies the input- and output buffer of the encoder and decoder and have an
effect directly to the delay.
.!.
We recommend a VBV buffer size of 2500 msec for safe operation.
.!.
For a small delay you can set the VBV buffer up to 800
msec., but complex video content may lead to a buffer overflow
and a corrupt stream.
.!.
The VBV buffer, the enabled padding
mode
and
the
transport rate affect each other and the
resulting video. Therefore
we recommend the following:
Big VBV buffer value
→ Small
transport rate value
Small VBV buffer value
→ Big transport rate value
.!.
This field have only an effect when padding is ‘ON’.
Profile:
Specifies the used profile. Profiles specify the syntax (i.e. algorithms) of the
video codec. You can select between:
Baseline
