[FFmpeg-devel] Questions about Video Memory in qsv decoders

Ivan Uskov ivan.uskov at nablet.com
Sat Jul 23 23:19:59 EEST 2016

Hello 张玉晓,

Friday, July 22, 2016, 4:10:36 AM, you wrote:

张> I have a question when learning ffmpeg qsv decoder and Intel media sdk.

张> The intel media sdk suggest to use Video Memory while doing Hardware
张> decoding, use System Memory while doing Software decoding.

张> FFmpeg only used System Memory to decode with qsv (Intel msdk) in file
张> libavcodec/qsvdec.c. Is there any problem when use Video Memory? 

As qsv modules maintainer I can confirm, yes, there are problems.

First (objective) problem that in common case there are 3 qsv components
should be linked by a pipeline through GPU memory: 
*qsv video decoder
*qsv vpp filter
*qsv video encoder
But current ffmpeg architecture have restrictions to share one common qsv
session between libavcodec and libavfilter.

Second  (subjective) problem that nobody in ffmpeg community is interested to
advance  QSV  codecs. Most of  patches at this year provided by me or by my
colleagues (including tries to solve issue with GPU memory) were rejected or
ignored silently. Moreover, if you will try to clone a latest ffmpeg you found qsv
decoder broken, it crashes at any try of use. The patch to fix it was posted
by me at April 25 but was ignored.

If it is acceptable for your purposes I would like to recommend you to look
libav. The qsv-related modules in libav should be more advanced this time.

Best regards,
 Ivan                            mailto:ivan.uskov at nablet.com

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