[FFmpeg-user] RES: A question on the Quadro P6000 and maximum simultaneous NVENC encodes in FFmpeg

[Yang Zhang]

for some reason, the developer called it cuvid, but nvidia called it
nvdec. so there is -hwaccel nvdec is a wrong option.

On 8/24/18, Dennis Mungai <dmngaie at gmail.com> wrote:
> For full GPU transcoding, shouldn't -hwaccel be nvdec?
>
> FFmpeg's documentation on this is missing, but for NVENC, the decoder
> should be set to nvdec.
>
> On Fri, 24 Aug 2018 at 01:24, Yang Zhang <yzfedora at gmail.com> wrote:
>
>> If you didn't specify -hwaccel option, then the full gpu transcoding
>> is disabled. for example:
>>
>> 1. full gpu transcoding.
>> $ ffmpeg -hwaccel cuvid -c:v h264_cuvid -i test.ts -c:v h264_nvenc ...
>>
>> 2. gpu transcoding via memory copy.
>> $ ffmpeg -c:v h264_cuvid -i test.ts -c:v h264_nvenc ...
>>
>> 3. cpu decoding and gpu encoding.
>> $ ffmpeg -i test.ts -c:v h264_nvenc ...
>>
>>
>>
>> On 8/24/18, Dennis Mungai <dmngaie at gmail.com> wrote:
>> > Is it possible to disable hwaccel decode explicitly in an FFmpeg
>> instance?
>> >
>> > Say, -hwaccel none such that no hardware-accelerated decoder instance is
>> > initialized on launch?
>> >
>> >
>> >
>> > On Fri, 24 Aug 2018 at 01:14, Yang Zhang <yzfedora at gmail.com> wrote:
>> >
>> >> Yes, 25 hd1080p channels use -hwaccel cuvid options to do full hardware
>> >> acceleration transcoding. other channels use the GPU encoding only.
>> >> this
>> >> should can let you transcoding more channels. and fix the stutter
>> problem.
>> >>
>> >> You can use "nvidia-smi dmon" to check the usage of NVDEC/ENC chips.
>> >>
>> >> On Fri, Aug 24, 2018 at 6:02 AM Dennis Mungai <dmngaie at gmail.com>
>> wrote:
>> >>
>> >> > So, to clarify:
>> >> >
>> >> > If you were to disable hwaccel decode (and rely solely on
>> software-based
>> >> > decoding) BUT utilize NVENC on a system with a beefy processor and
>> >> adequate
>> >> > RAM, you should be able to eliminate the bottleneck, correct?
>> >> >
>> >> > Because what you're implying (by the bottleneck at decode side) would
>> be
>> >> a
>> >> > limitation in how FFmpeg handles filter performance (hwupload, to be
>> >> > exact), an issue that can be circumvented by eliminating hwaccel in
>> >> decode.
>> >> >
>> >> >
>> >> >
>> >> > On Fri, 24 Aug 2018 at 00:57, Yang Zhang <yzfedora at gmail.com> wrote:
>> >> >
>> >> > > The problem is even you using the Tesla P100, and you can see it
>> has 3
>> >> > > NVENC chips inside it. but it has only 1 NVDEC chip, this is very
>> very
>> >> > > important. the bottleneck is at decoding side. this is why you got
>> >> > freezing
>> >> > > or stutter problem. basically, perhaps you can use Tesla P100
>> encoding
>> >> 75
>> >> > > hd1080p channels, but you can not decoding more than 25 hd1080p
>> >> channels
>> >> > on
>> >> > > it.
>> >> > >
>> >> > > On Fri, Aug 24, 2018 at 5:51 AM Dennis Mungai <dmngaie at gmail.com>
>> >> wrote:
>> >> > >
>> >> > > > No.
>> >> > > >
>> >> > > > This is as tested on the Tesla P100.
>> >> > > >
>> >> > > > On Fri, 24 Aug 2018 at 00:26, Pedro Daniel Costa <
>> >> > > > portalnet2 at outlook.com.br>
>> >> > > > wrote:
>> >> > > >
>> >> > > > > Ok
>> >> > > > >
>> >> > > > > But with the TESLA models, did you have any issues over 40
>> >> > > > > streams?
>> >> > > > >
>> >> > > > > I am planning on budge project to run minimum 100channels
>> >> > > > >
>> >> > > > > -----Mensagem original-----
>> >> > > > > De: ffmpeg-user [mailto:ffmpeg-user-bounces at ffmpeg.org] Em
>> nome de
>> >> > > > Dennis
>> >> > > > > Mungai
>> >> > > > > Enviada em: quinta-feira, 23 de agosto de 2018 13:54
>> >> > > > > Para: FFmpeg user questions
>> >> > > > > Assunto: [FFmpeg-user] A question on the Quadro P6000 and
>> maximum
>> >> > > > > simultaneous NVENC encodes in FFmpeg
>> >> > > > >
>> >> > > > > Hello there,
>> >> > > > >
>> >> > > > > For users with this specific card (and FFmpeg installed),
>> >> > > > > kindly
>> >> > > clarify
>> >> > > > > on the following:
>> >> > > > >
>> >> > > > > (a). How many simultaneous encoder sessions can you run on this
>> >> card?
>> >> > > > >
>> >> > > > > (b). Have you ran into any issues, such as stuttering and
>> dropping
>> >> > > > streams
>> >> > > > > with multiple concurrent encodes?
>> >> > > > >
>> >> > > > > I ask because of a recent case where adding more than ~40
>> >> concurrent
>> >> > > > > encodes would make the output "drop" and stutter massively, as
>> if
>> >> > > FFmpeg
>> >> > > > > itself was hanging, despite the GPU having more than enough
>> >> > > > > VRAM
>> >> > > (24GB?)
>> >> > > > > and resources (under ~11% utilization according to nvidia-smi),
>> >> > > implying
>> >> > > > > some sort of artificial limitation in effect despite the GPU
>> >> support
>> >> > > > matrix
>> >> > > > > specifying otherwise:
>> >> > > > >
>> >> https://developer.nvidia.com/video-encode-decode-gpu-support-matrix
>> >> > > > >
>> >> > > > > Your feedback on this is appreciated.
>> >> > > > > _______________________________________________
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>> >> > > > >
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