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Rennes Emotion Map 2010-11
19 octobre 2011, par
Mis à jour : Juillet 2013
Langue : français
Type : Texte
Autres articles (102)
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Sur d’autres sites (10021)
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rtpdec_jpeg : fix low contrast image on low quality setting
24 mars 2016, par Ico Doornekamprtpdec_jpeg : fix low contrast image on low quality setting
The problem is that the argument ’q’ is of the type uint8_t.
According to the JPEG standard, if 1 <= q <= 50, the scale factor
’S’ should be 5000 / Q. Because the create_default_qtables() reuses
the variable ’q’ to store the result of this calculation, for small
values of q < 19, q wil subsequently overflow and give wrong results
in the calculated quantization tables.Instead, use a new variable ’S’ (same name as in RFC2435) with the
proper range to store the result of the division.Signed-off-by : Martin Storsjö <martin@martin.st>
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avformat/rtpdec_jpeg : fix low contrast image on low quality setting
24 mars 2016, par Ico Doornekampavformat/rtpdec_jpeg : fix low contrast image on low quality setting
Original mail and my own followup on ffmpeg-user earlier today :
I have a device sending out a MJPEG/RTP stream on a low quality setting.
Decoding and displaying the video with libavformat results in a washed
out, low contrast, greyish image. Playing the same stream with VLC results
in proper color representation.Screenshots for comparison :
http://zevv.nl/div/libav/shot-ffplay.jpg
http://zevv.nl/div/libav/shot-vlc.jpgA pcap capture of a few seconds of video and SDP file for playing the
stream are available athttp://zevv.nl/div/libav/mjpeg.pcap
http://zevv.nl/div/libav/mjpeg.sdpI believe the problem might be in the calculation of the quantization
tables in the function create_default_qtables(), the attached patch
solves the issue for me.The problem is that the argument ’q’ is of the type uint8_t. According to the
JPEG standard, if 1 <= q <= 50, the scale factor ’S’ should be 5000 / Q.
Because the create_default_qtables() reuses the variable ’q’ to store the
result of this calculation, for small values of q < 19, q wil subsequently
overflow and give wrong results in the calculated quantization tables. The
patch below uses a new variable ’S’ (same name as in RFC2435) with the proper
range to store the result of the division.Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
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I have an application in flask where it streams a camera using ffmpeg, the problem is that I can not display the video from the camera using the GPU [closed]
17 janvier, par RubenI'll put you in context, I am using flask (python) to display a camera in the browser to stream it, for this I use the following Python code :


command = [
 'ffmpeg',
 '-loglevel', 'warning',
 '-rtsp_transport', 'tcp',
 '-i', self.config['url'],
 '-map', '0:v:0', # fuerzo que solo procese el video
 '-vf', f'fps={self.config["fps"]},scale=640:360:force_original_aspect_ratio=decrease',
 '-c:v', 'h264_nvenc', # especificamos que queremos tirar de la gpu de nvidia
 '-preset', 'p7', # ajusta para la maxima calidad/velocidad (p1 mas rapida pero peor calidad - p7 más lento pero mejor calidad)
 '-qp', self.config['quality'], # control de calidad del codificador (0 [mejor calidad] - 51 [peor calidad])
 '-pix_fmt', 'yuv444p', # se mete explicitamente el formato de pixeles
 '-color_range', 'pc',
 '-an', # desactiva el audio
 '-f', 'image2pipe',
 'pipe:1'
] 

self.process = subprocess.Popen(
 command,
 stdout=subprocess.PIPE,
 stderr=subprocess.PIPE,
 bufsize=10**8
)


The problem is that it does not display the video streaming, but it connects correctly to the camera.


On the other hand, It show me the following warnings, which may have something to do with the display, it's probably the second warning that has to do with the pixel format :


DEBUG :main:FFmpeg [camera1] : Guessed Channel Layout for Input Stream #0.1 : mono
DEBUG :main:FFmpeg [camera1] : [swscaler @ 0x560f70b78680] deprecated pixel format used, make sure you did set range correctly


The server has different encodes installed :


DEV.LS h264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders : h264 h264_v4l2m2m h264_qsv h264_cuvid ) (encoders : libx264 libx264rgb h264_nvenc h264_omx h264_qsv h264_v4l2m2m h264_vaapi nvenc nvenc_h264 )


Y uso el h264_nvenc, tambien el servidor tiene soporte de aceleración de hardware con :


libavutil 56. 70.100 / 56. 70.100
libavcodec 58.134.100 / 58.134.100
libavformat 58. 76.100 / 58. 76.100
libavdevice 58. 13.100 / 58. 13.100
libavfilter 7.110.100 / 7.110.100
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100
Hardware acceleration methods :
vdpau
cuda
vaapi
qsv
drm
opencl


Between them h264_nvenc uses cuda


I expand a little on the information it provides me when using h264_nvenc :


Encoder h264_nvenc [NVIDIA NVENC H.264 encoder]:
 General capabilities: dr1 delay hardware
 Threading capabilities: none
 Supported hardware devices: cuda cuda
 Supported pixel formats: yuv420p nv12 p010le yuv444p p016le yuv444p16le bgr0 rgb0 cuda
h264_nvenc AVOptions:
 -preset <int> E..V....... Set the encoding preset (from 0 to 18) (default p4)
 default 0 E..V.......
 slow 1 E..V....... hq 2 passes
 medium 2 E..V....... hq 1 pass
 fast 3 E..V....... hp 1 pass
 hp 4 E..V.......
 hq 5 E..V.......
 bd 6 E..V.......
 ll 7 E..V....... low latency
 llhq 8 E..V....... low latency hq
 llhp 9 E..V....... low latency hp
 lossless 10 E..V.......
 losslesshp 11 E..V.......
 p1 12 E..V....... fastest (lowest quality)
 p2 13 E..V....... faster (lower quality)
 p3 14 E..V....... fast (low quality)
 p4 15 E..V....... medium (default)
 p5 16 E..V....... slow (good quality)
 p6 17 E..V....... slower (better quality)
 p7 18 E..V....... slowest (best quality)
 -tune <int> E..V....... Set the encoding tuning info (from 1 to 4) (default hq)
 hq 1 E..V....... High quality
 ll 2 E..V....... Low latency
 ull 3 E..V....... Ultra low latency
 lossless 4 E..V....... Lossless
 -profile <int> E..V....... Set the encoding profile (from 0 to 3) (default main)
 baseline 0 E..V.......
 main 1 E..V.......
 high 2 E..V.......
 high444p 3 E..V.......
 -level <int> E..V....... Set the encoding level restriction (from 0 to 62) (default auto)
 auto 0 E..V.......
 1 10 E..V.......
 1.0 10 E..V.......
 1b 9 E..V.......
 1.0b 9 E..V.......
 1.1 11 E..V.......
 1.2 12 E..V.......
 1.3 13 E..V.......
 2 20 E..V.......
 2.0 20 E..V.......
 2.1 21 E..V.......
 2.2 22 E..V.......
 3 30 E..V.......
 3.0 30 E..V.......
 3.1 31 E..V.......
 3.2 32 E..V.......
 4 40 E..V.......
 4.0 40 E..V.......
 4.1 41 E..V.......
 4.2 42 E..V.......
 5 50 E..V.......
 5.0 50 E..V.......
 5.1 51 E..V.......
 5.2 52 E..V.......
 6.0 60 E..V.......
 6.1 61 E..V.......
 6.2 62 E..V.......
 -rc <int> E..V....... Override the preset rate-control (from -1 to INT_MAX) (default -1)
 constqp 0 E..V....... Constant QP mode
 vbr 1 E..V....... Variable bitrate mode
 cbr 2 E..V....... Constant bitrate mode
 vbr_minqp 8388612 E..V....... Variable bitrate mode with MinQP (deprecated)
 ll_2pass_quality 8388616 E..V....... Multi-pass optimized for image quality (deprecated)
 ll_2pass_size 8388624 E..V....... Multi-pass optimized for constant frame size (deprecated)
 vbr_2pass 8388640 E..V....... Multi-pass variable bitrate mode (deprecated)
 cbr_ld_hq 8388616 E..V....... Constant bitrate low delay high quality mode
 cbr_hq 8388624 E..V....... Constant bitrate high quality mode
 vbr_hq 8388640 E..V....... Variable bitrate high quality mode
 -rc-lookahead <int> E..V....... Number of frames to look ahead for rate-control (from 0 to INT_MAX) (default 0)
 -surfaces <int> E..V....... Number of concurrent surfaces (from 0 to 64) (default 0)
 -cbr <boolean> E..V....... Use cbr encoding mode (default false)
 -2pass <boolean> E..V....... Use 2pass encoding mode (default auto)
 -gpu <int> E..V....... Selects which NVENC capable GPU to use. First GPU is 0, second is 1, and so on. (from -2 to INT_MAX) (default any)
 any -1 E..V....... Pick the first device available
 list -2 E..V....... List the available devices
 -delay <int> E..V....... Delay frame output by the given amount of frames (from 0 to INT_MAX) (default INT_MAX)
 -no-scenecut <boolean> E..V....... When lookahead is enabled, set this to 1 to disable adaptive I-frame insertion at scene cuts (default false)
 -forced-idr <boolean> E..V....... If forcing keyframes, force them as IDR frames. (default false)
 -b_adapt <boolean> E..V....... When lookahead is enabled, set this to 0 to disable adaptive B-frame decision (default true)
 -spatial-aq <boolean> E..V....... set to 1 to enable Spatial AQ (default false)
 -spatial_aq <boolean> E..V....... set to 1 to enable Spatial AQ (default false)
 -temporal-aq <boolean> E..V....... set to 1 to enable Temporal AQ (default false)
 -temporal_aq <boolean> E..V....... set to 1 to enable Temporal AQ (default false)
 -zerolatency <boolean> E..V....... Set 1 to indicate zero latency operation (no reordering delay) (default false)
 -nonref_p <boolean> E..V....... Set this to 1 to enable automatic insertion of non-reference P-frames (default false)
 -strict_gop <boolean> E..V....... Set 1 to minimize GOP-to-GOP rate fluctuations (default false)
 -aq-strength <int> E..V....... When Spatial AQ is enabled, this field is used to specify AQ strength. AQ strength scale is from 1 (low) - 15 (aggressive) (from 1 to 15) (default 8)
 -cq <float> E..V....... Set target quality level (0 to 51, 0 means automatic) for constant quality mode in VBR rate control (from 0 to 51) (default 0)
 -aud <boolean> E..V....... Use access unit delimiters (default false)
 -bluray-compat <boolean> E..V....... Bluray compatibility workarounds (default false)
 -init_qpP <int> E..V....... Initial QP value for P frame (from -1 to 51) (default -1)
 -init_qpB <int> E..V....... Initial QP value for B frame (from -1 to 51) (default -1)
 -init_qpI <int> E..V....... Initial QP value for I frame (from -1 to 51) (default -1)
 -qp <int> E..V....... Constant quantization parameter rate control method (from -1 to 51) (default -1)
 -weighted_pred <int> E..V....... Set 1 to enable weighted prediction (from 0 to 1) (default 0)
 -coder <int> E..V....... Coder type (from -1 to 2) (default default)
 default -1 E..V.......
 auto 0 E..V.......
 cabac 1 E..V.......
 cavlc 2 E..V.......
 ac 1 E..V.......
 vlc 2 E..V.......
 -b_ref_mode <int> E..V....... Use B frames as references (from 0 to 2) (default disabled)
 disabled 0 E..V....... B frames will not be used for reference
 each 1 E..V....... Each B frame will be used for reference
 middle 2 E..V....... Only (number of B frames)/2 will be used for reference
 -a53cc <boolean> E..V....... Use A53 Closed Captions (if available) (default true)
 -dpb_size <int> E..V....... Specifies the DPB size used for encoding (0 means automatic) (from 0 to INT_MAX) (default 0)
 -multipass <int> E..V....... Set the multipass encoding (from 0 to 2) (default disabled)
 disabled 0 E..V....... Single Pass
 qres 1 E..V....... Two Pass encoding is enabled where first Pass is quarter resolution
 fullres 2 E..V....... Two Pass encoding is enabled where first Pass is full resolution
 -ldkfs <int> E..V....... Low delay key frame scale; Specifies the Scene Change frame size increase allowed in case of single frame VBV and CBR (from 0 to 255) (default 0)
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If anyone has some idea or needs more information to help me, I would appreciate it.


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