DSP Support Forum : FAQ List - All Communities

Why does the video sometime become jumpy on the screen when using the video decoders?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 05:11:23 GMT

This may occur sometimes due to very high USB MIPs espcially when many applications excute in the background to perform data transfer over the USB bus. USB MIPs usage can be profiled across fread functions and user must ensure that USB MIPs does not become very high during normal operations of the video decoders.

Can the video CODECs be run on multiple Blackfin processors to do high bit rate sequences?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 05:01:03 GMT

Yes it is possible to run the encoders on Blackfin processors or cores to increase performance. However, the decoders are not designed to do the same and can only run on a single Blackfin processor or core. Their performance is limited by the MIPs offered by the single processor/core so for more details on MIPs refer to the decoder Product Specification which is provided in the decoder package when installed.

Can encoding and decoding occur simultaneously on Blackfin processors?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:57:01 GMT

Yes, simultaneous encoding and decoding may be done on Blackfin however presently there is not such demo application available a user must write their own such application.

To save MIPs, do the MPEG-4 and H.264 encoders support "only gray-scale (ie luma only)" encoding?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:40:10 GMT

It is not possible to encode "only-gray scale" with the MPEG-4 SP/ASP encoder library since MPEG-4doesn't support it. However, it is possible to interface a B&W camera capable of outputing only "Luma" data. If such a camera is used then the application must fill the "u" and "v" data in the PPI input buffer with 128(for the color component to be 0) before it passed into the encoder. Note that there is no saving on the encoder bandwidth but PPI bandwidth is saved.

The H.264 BP encoder does support "only-Gray scale" (Luma-only) encoding.

Is it possible tp flash my code onto the Blackfin?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:35:19 GMT

Yes it is possible to flash code onto the Blackfin processors. Instrcutions are provided in the VisualDSP++ manuals on how to create a loader file. Also refer to the instructions provided with the EZ KIT manuals on how to flash the code.

Can I do Scaling on the decoded output from the video decoders?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:25:45 GMT

The MPEG-2,MPEG-4 SP/ASP and Windows Media Video (WMV9) Standarddecoder libraries all have scaling capabilities. A user may add custom code for scaling using the post processing API interface in the MPEG-4 SP/ASP or MPEG-2video decoders only. User provided custom APIs must be written and passed into the library as callback functions. Post processing APIs are not currently available in the H.264 BP decoder.

Can I do Scaling/Region of Interest encoding with the video encoders?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:21:30 GMT

Yes the MPEG-4 SP/ASP and H.264 BP encoders do support Scaling/Region of Interest Encoding for YUV422 input. The H.264 BP/MP encoder supports Scaling/Region of Interest encoding for YUV420 input.

Is post processing supported with the video decoders and is it possible to add custom post processing modules to the framework?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:11:47 GMT

Yes, all the following decoder contain post processing capabilities internally in the library:

H.264 BP decode
MPEG-2 decoder
MPEG-4 SP/ASP decoder,
Windows Media Video (WMV9) Standard Decoder

Only MPEG-2 and MPEG-4 SP/ASP decoders support external post processing interfaces so that custom post processing modules may be added. Example code is provided for CCIRBT.656, RGB565 and RGB888 color conversions.

Why doesn't the default output of the H.264 BP encoder carry frame rate information?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 04:03:41 GMT

According to the H.264 standard or MPEG-4 part-10 (ISO/IEC 14496-10:2005(E) standard), the frame rate (fps) information is NOT mandatory in the H.264 Sequencer Parameter Set (SPS) as a result older encoders did not present it. Releases after Rel 3.0.0 of the H.264 BP/MP encoder does provide this information.

Why does the default output from my encoder not play with correct aspect ratio?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 03:55:12 GMT

This issue is seen with the earlier releases (Rel 2.1.0 and before) of the H.264 BP encoder which was fixed in later versions after release 2.1.0. However, if this issues is still encountered then you will have to configure the player to ignore the aspect ratio present in the bit stream. For example if you are using mplayer then use the -noaspect switch on command line.

What encoders may I use to create video streams for testing the decoders?

analog@sgaur.hosted.jivesoftware.com — Sun, 08 Nov 2009 03:47:12 GMT

Envivio - It is a commercially available encoder which may be purchased at www.envivio.com.
ffmpeg - It is used to create MPEG-2, MPEG-4 and H.264 video content. Is is available at http://ffmpeg.org/download.html.
H.264 Reference Encoder - It is used to create H.264 content and may obtained at http://standards.iso.org/ittf/PubliclyAvailableStandards.
MPEG-4 Reference Encoder - It is used to create MPEG-4 content and may obtained at http://standards.iso.org/ittf/PubliclyAvailableStandards.
MPEG-2 Reference Encoder - It is used to create MPEG-2 content and may obtained at http://standards.iso.org/ittf/PubliclyAvailableStandards.