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FFmpeg : unspecified pixel format when opening video with custom context
14 février 2021, par PedroI am trying to decode a video with a custom context. The purpose is that I want to decode the video directly from memory. In the following code, I am reading from file in the
readfunction passed toavio_alloc_context- but this is just for testing purposes.


I think I've read any post there is on Stackoverflow or on any other website related to this topic. At least I definitely tried my best to do so. While there is much in common, the details differ : people set different flags, some say
av_probe_input_formatis required, some say it isn't, etc. And for some reason nothing works for me.


My problem is that the pixel format is unspecified (see output below), which is why I run into problems later when calling
sws_getContext. I checkedpFormatContext->streams[videoStreamIndex]->codec->pix_fmt, and it is -1.


Please note my comments
// things I triedand// seems not to helpin the code. I think, the answer might be hidden somehwere there. I tried many combinations of hints that I've read so far, but I am missing a detail I guess.


The problem is not the video file, because when I go the standard way and just call
avformat_open_input(&pFormatContext, pFilePath, NULL, NULL)without a custom context, everything runs fine.


The code compiles and runs as is.



#include <libavformat></libavformat>avformat.h>
#include 
#include 

FILE *f;

static int read(void *opaque, uint8_t *buf, int buf_size) {
 if (feof(f)) return -1;
 return fread(buf, 1, buf_size, f);
}

int openVideo(const char *pFilePath) {
 const int bufferSize = 32768;
 int ret;

 av_register_all();

 f = fopen(pFilePath, "rb");
 uint8_t *pBuffer = (uint8_t *) av_malloc(bufferSize + AVPROBE_PADDING_SIZE);
 AVIOContext *pAVIOContext = avio_alloc_context(pBuffer, bufferSize, 0, NULL,
 &read, NULL, NULL);

 if (!f || !pBuffer || !pAVIOContext) {
 printf("error: open / alloc failed\n");
 // cleanup...
 return 1;
 }

 AVFormatContext *pFormatContext = avformat_alloc_context();
 pFormatContext->pb = pAVIOContext;

 const int readBytes = read(NULL, pBuffer, bufferSize);

 printf("readBytes = %i\n", readBytes);

 if (readBytes <= 0) {
 printf("error: read failed\n");
 // cleanup...
 return 2;
 }

 if (fseek(f, 0, SEEK_SET) != 0) {
 printf("error: fseek failed\n");
 // cleanup...
 return 3;
 }

 // required for av_probe_input_format
 memset(pBuffer + readBytes, 0, AVPROBE_PADDING_SIZE);

 AVProbeData probeData;
 probeData.buf = pBuffer;
 probeData.buf_size = readBytes;
 probeData.filename = "";
 probeData.mime_type = NULL;

 pFormatContext->iformat = av_probe_input_format(&probeData, 1);

 // things I tried:
 //pFormatContext->flags = AVFMT_FLAG_CUSTOM_IO;
 //pFormatContext->iformat->flags |= AVFMT_NOFILE;
 //pFormatContext->iformat->read_header = NULL;

 // seems not to help (therefore commented out here):
 AVDictionary *pDictionary = NULL;
 //av_dict_set(&pDictionary, "analyzeduration", "8000000", 0);
 //av_dict_set(&pDictionary, "probesize", "8000000", 0);

 if ((ret = avformat_open_input(&pFormatContext, "", NULL, &pDictionary)) < 0) {
 char buffer[4096];
 av_strerror(ret, buffer, sizeof(buffer));
 printf("error: avformat_open_input failed: %s\n", buffer);
 // cleanup...
 return 4;
 }

 printf("retrieving stream information...\n");

 if ((ret = avformat_find_stream_info(pFormatContext, NULL)) < 0) {
 char buffer[4096];
 av_strerror(ret, buffer, sizeof(buffer));
 printf("error: avformat_find_stream_info failed: %s\n", buffer);
 // cleanup...
 return 5;
 }

 printf("nb_streams = %i\n", pFormatContext->nb_streams);

 // further code...

 // cleanup...
 return 0;
}

int main() {
 openVideo("video.mp4");
 return 0;
}



This is the output that I get :

readBytes = 32768

retrieving stream information...

[mov,mp4,m4a,3gp,3g2,mj2 @ 0xdf8d20] stream 0, offset 0x30 : partial file
[mov,mp4,m4a,3gp,3g2,mj2 @ 0xdf8d20] Could not find codec parameters for stream 0 (Video : h264 (avc1 / 0x31637661), none, 640x360, 351 kb/s) : unspecified pixel format

Consider increasing the value for the 'analyzeduration' and 'probesize' options

nb_streams = 2


UPDATE :

Thanks to WLGfx, here is the solution : The only thing that was missing was the seek function. Apparently, implementing it is mandatory for decoding. It is important to return the new offset - and not 0 in case of success (some solutions found in the web just return the return value of fseek, and that is wrong). Here is the minimal solution that made it work :


static int64_t seek(void *opaque, int64_t offset, int whence) {
 if (whence == SEEK_SET && fseek(f, offset, SEEK_SET) == 0) {
 return offset;
 }
 // handling AVSEEK_SIZE doesn't seem mandatory
 return -1;
}



Of course, the call to
avio_alloc_contextneeds to be adapted accordingly :


AVIOContext *pAVIOContext = avio_alloc_context(pBuffer, bufferSize, 0, NULL,
 &read, NULL, &seek);


-
Rust Win32 FFI : User-mode data execution prevention (DEP) violation
28 avril 2022, par TheElixI'm trying to pass a ID3D11Device instance from Rust to a C FFI Library (FFMPEG).


I made this sample code :


pub fn create_d3d11_device(&mut self, device: &mut Box, context: &mut Box) {
 let av_device : Box<avbufferref> = self.alloc(HwDeviceType::D3d11va);
 unsafe {
 let device_context = Box::from_raw(av_device.data as *mut AVHWDeviceContext);
 let mut d3d11_device_context = Box::from_raw(device_context.hwctx as *mut AVD3D11VADeviceContext);
 d3d11_device_context.device = device.as_mut() as *mut _;
 d3d11_device_context.device_context = context.as_mut() as *mut _;
 let avp = Box::into_raw(av_device);
 av_hwdevice_ctx_init(avp);
 self.av_hwdevice = Some(Box::from_raw(avp));
 }
 }
</avbufferref>

On the Rust side the Device does work, but on the C side, when FFMEPG calls
ID3D11DeviceContext_QueryInterfacethe app crashes with the following error :Exception 0xc0000005 encountered at address 0x7ff9fb99ad38: User-mode data execution prevention (DEP) violation at location 0x7ff9fb99ad38

The address is actually the pointer for the lpVtbl of QueryInterface, like seen here :


The disassembly of the address also looks correct (this is done on an another debugging session) :


(lldb) disassemble --start-address 0x00007ffffdf3ad38
 0x7ffffdf3ad38: addb %ah, 0x7ffffd(%rdi,%riz,8)
 0x7ffffdf3ad3f: addb %al, (%rax)
 0x7ffffdf3ad41: movabsl -0x591fffff80000219, %eax
 0x7ffffdf3ad4a: outl %eax, $0xfd


Do you have any pointer to debug this further ?


EDIT : I made a Minimal Reproducion Sample. Interestingly this does not causes a DEP Violation, but simply a Segfault.


On the C side :


int test_ffi(ID3D11Device *device){
 ID3D11DeviceContext *context;
 device->lpVtbl->GetImmediateContext(device, &context);
 if (!context) return 1;
 return 0;
}


On the Rust side :


unsafe fn main_rust(){
 let mut device = None;
 let mut device_context = None;
 let _ = match windows::Win32::Graphics::Direct3D11::D3D11CreateDevice(None, D3D_DRIVER_TYPE_HARDWARE, OtherHinstance::default(), D3D11_CREATE_DEVICE_DEBUG, &[], D3D11_SDK_VERSION, &mut device, std::ptr::null_mut(), &mut device_context) {
 Ok(e) => e,
 Err(e) => panic!("Creation Failed: {}", e)
 };
 let mut device = match device {
 Some(e) => e,
 None => panic!("Creation Failed2")
 };
 let mut f2 : ID3D11Device = transmute_copy(&device); //Transmuting the WinAPI into a bindgen ID3D11Device
 test_ffi(&mut f2);
}


The bindgen build.rs :


extern crate bindgen;

use std::env;
use std::path::PathBuf;

fn main() {
 // Tell cargo to tell rustc to link the system bzip2
 // shared library.
 println!("cargo:rustc-link-lib=ffi_demoLIB");
 println!("cargo:rustc-link-lib=d3d11");

 // Tell cargo to invalidate the built crate whenever the wrapper changes
 println!("cargo:rerun-if-changed=library.h");

 // The bindgen::Builder is the main entry point
 // to bindgen, and lets you build up options for
 // the resulting bindings.
 let bindings = bindgen::Builder::default()
 // The input header we would like to generate
 // bindings for.
 .header("library.h")
 // Tell cargo to invalidate the built crate whenever any of the
 // included header files changed.
 .parse_callbacks(Box::new(bindgen::CargoCallbacks))
 .blacklist_type("_IMAGE_TLS_DIRECTORY64")
 .blacklist_type("IMAGE_TLS_DIRECTORY64")
 .blacklist_type("PIMAGE_TLS_DIRECTORY64")
 .blacklist_type("IMAGE_TLS_DIRECTORY")
 .blacklist_type("PIMAGE_TLS_DIRECTORY")
 // Finish the builder and generate the bindings.
 .generate()
 // Unwrap the Result and panic on failure.
 .expect("Unable to generate bindings");

 // Write the bindings to the $OUT_DIR/bindings.rs file.
 let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
 bindings
 .write_to_file(out_path.join("bindings.rs"))
 .expect("Couldn't write bindings!");
}


The Complete Repo can be found over here : https://github.com/TheElixZammuto/demo-ffi


-
Frames took with ELP camera has unknown pixel format at FHD ?
11 novembre 2024, par Marcel KoperaI'm trying to take a one frame ever x seconds from my usb camera. Name of the camera is : ELP-USBFHD06H-SFV(5-50).
Code is not 100% done yet, but I'm using it this way right now ↓ (
shotfn is called frommain.pyin a loop)


import cv2
import subprocess

from time import sleep
from collections import namedtuple

from errors import *

class Camera:
 def __init__(self, cam_index, res_width, res_height, pic_format, day_time_exposure_ms, night_time_exposure_ms):
 Resolution = namedtuple("resolution", ["width", "height"])
 self.manual_mode(True)

 self.cam_index = cam_index
 self.camera_resolution = Resolution(res_width, res_height)
 self.picture_format = pic_format
 self.day_time_exposure_ms = day_time_exposure_ms
 self.night_time_exposure_ms = night_time_exposure_ms

 self.started: bool = False
 self.night_mode = False

 self.cap = cv2.VideoCapture(self.cam_index, cv2.CAP_V4L2)
 self.cap.set(cv2.CAP_PROP_FRAME_WIDTH, self.camera_resolution.width)
 self.cap.set(cv2.CAP_PROP_FRAME_HEIGHT, self.camera_resolution.height)
 self.cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc(*self.picture_format))

 

 def start(self):
 sleep(1)
 if not self.cap.isOpened():
 return CameraCupError()

 self.set_exposure_time(self.day_time_exposure_ms)
 self.set_brightness(0)
 sleep(0.1)
 
 self.started = True



 def shot(self, picture_name, is_night):
 if not self.started:
 return InitializationError()

 self.configure_mode(is_night)

 # Clear buffer
 for _ in range(5):
 ret, _ = self.cap.read()

 ret, frame = self.cap.read()

 sleep(0.1)

 if ret:
 print(picture_name)
 cv2.imwrite(picture_name, frame)
 return True

 else:
 print("No photo")
 return False


 
 def release(self):
 self.set_exposure_time(156)
 self.set_brightness(0)
 self.manual_mode(False)
 self.cap.release()



 def manual_mode(self, switch: bool):
 if switch:
 subprocess.run(["v4l2-ctl", "--set-ctrl=auto_exposure=1"])
 else:
 subprocess.run(["v4l2-ctl", "--set-ctrl=auto_exposure=3"])
 sleep(1)

 
 
 def configure_mode(self, is_night):
 if is_night == self.night_mode:
 return

 if is_night:
 self.night_mode = is_night
 self.set_exposure_time(self.night_time_exposure_ms)
 self.set_brightness(64)
 else:
 self.night_mode = is_night
 self.set_exposure_time(self.day_time_exposure_ms)
 self.set_brightness(0)
 sleep(0.1)



 def set_exposure_time(self, ms: int):
 ms = int(ms)
 default_val = 156

 if ms < 1 or ms > 5000:
 ms = default_val

 self.cap.set(cv2.CAP_PROP_EXPOSURE, ms)



 def set_brightness(self, value: int):
 value = int(value)
 default_val = 0

 if value < -64 or value > 64:
 value = default_val

 self.cap.set(cv2.CAP_PROP_BRIGHTNESS, value)


Here are settings for the camera (yaml file)


camera:
 camera_index: 0
 res_width: 1920
 res_height: 1080
 picture_format: "MJPG"
 day_time_exposure_ms: 5
 night_time_exposure_ms: 5000
 photos_format: "jpg"



I do some configs like set manual mode for the camera, change exposure/brightness and saving frame.
Also the camera is probably catching the frames to the buffer (it is not saving latest frame in real time : it's more laggish), so I have to clear buffer every time. like this


# Clear buffer from old frames
 for _ in range(5):
 ret, _ = self.cap.read()
 
 # Get a new frame
 ret, frame = self.cap.read()


What I really don't like, but I could find a better way (tldr : setting buffer for 1 frame doesn't work on my camera).


Frames saved this method looks good with 1920x1080 resolution. BUT when I try to run
ffmpegcommand to make a timelapse from savedjpgfile like this

ffmpeg -framerate 20 -pattern_type glob -i "*.jpg" -c:v libx264 output.mp4


I got an error like this one


[image2 @ 0x555609c45240] Could not open file : 08:59:20.jpg
[image2 @ 0x555609c45240] Could not find codec parameters for stream 0 (Video: mjpeg, none(bt470bg/unknown/unknown)): unspecified size
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options
Input #0, image2, from '*.jpg':
 Duration: 00:00:00.05, start: 0.000000, bitrate: N/A
 Stream #0:0: Video: mjpeg, none(bt470bg/unknown/unknown), 20 fps, 20 tbr, 20 tbn
Output #0, mp4, to 'output.mp4':
Output file #0 does not contain any stream


Also when I try to copy the files from Linux to Windows I get some weird copy failing error and option to skip the picture. But even when I press the skip button, the picture is copied and can be opened. I'm not sure what is wrong with the format, but the camera is supporting MPEG at 1920x1080.


>>> v4l2-ctl --all

Driver Info:
 Driver name : uvcvideo
 Card type : H264 USB Camera: USB Camera
 Bus info : usb-xhci-hcd.1-1
 Driver version : 6.6.51
 Capabilities : 0x84a00001
 Video Capture
 Metadata Capture
 Streaming
 Extended Pix Format
 Device Capabilities
 Device Caps : 0x04200001
 Video Capture
 Streaming
 Extended Pix Format
Media Driver Info:
 Driver name : uvcvideo
 Model : H264 USB Camera: USB Camera
 Serial : 2020032801
 Bus info : usb-xhci-hcd.1-1
 Media version : 6.6.51
 Hardware revision: 0x00000100 (256)
 Driver version : 6.6.51
Interface Info:
 ID : 0x03000002
 Type : V4L Video
Entity Info:
 ID : 0x00000001 (1)
 Name : H264 USB Camera: USB Camera
 Function : V4L2 I/O
 Flags : default
 Pad 0x0100000d : 0: Sink
 Link 0x0200001a: from remote pad 0x1000010 of entity 'Extension 4' (Video Pixel Formatter): Data, Enabled, Immutable
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
 Width/Height : 1920/1080
 Pixel Format : 'MJPG' (Motion-JPEG)
 Field : None
 Bytes per Line : 0
 Size Image : 4147789
 Colorspace : sRGB
 Transfer Function : Default (maps to sRGB)
 YCbCr/HSV Encoding: Default (maps to ITU-R 601)
 Quantization : Default (maps to Full Range)
 Flags :
Crop Capability Video Capture:
 Bounds : Left 0, Top 0, Width 1920, Height 1080
 Default : Left 0, Top 0, Width 1920, Height 1080
 Pixel Aspect: 1/1
Selection Video Capture: crop_default, Left 0, Top 0, Width 1920, Height 1080, Flags:
Selection Video Capture: crop_bounds, Left 0, Top 0, Width 1920, Height 1080, Flags:
Streaming Parameters Video Capture:
 Capabilities : timeperframe
 Frames per second: 15.000 (15/1)
 Read buffers : 0

User Controls

 brightness 0x00980900 (int) : min=-64 max=64 step=1 default=0 value=64
 contrast 0x00980901 (int) : min=0 max=64 step=1 default=32 value=32
 saturation 0x00980902 (int) : min=0 max=128 step=1 default=56 value=56
 hue 0x00980903 (int) : min=-40 max=40 step=1 default=0 value=0
 white_balance_automatic 0x0098090c (bool) : default=1 value=1
 gamma 0x00980910 (int) : min=72 max=500 step=1 default=100 value=100
 gain 0x00980913 (int) : min=0 max=100 step=1 default=0 value=0
 power_line_frequency 0x00980918 (menu) : min=0 max=2 default=1 value=1 (50 Hz)
 0: Disabled
 1: 50 Hz
 2: 60 Hz
 white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=4600 value=4600 flags=inactive
 sharpness 0x0098091b (int) : min=0 max=6 step=1 default=3 value=3
 backlight_compensation 0x0098091c (int) : min=0 max=2 step=1 default=1 value=1

Camera Controls

 auto_exposure 0x009a0901 (menu) : min=0 max=3 default=3 value=1 (Manual Mode)
 1: Manual Mode
 3: Aperture Priority Mode
 exposure_time_absolute 0x009a0902 (int) : min=1 max=5000 step=1 default=156 value=5000
 exposure_dynamic_framerate 0x009a0903 (bool) : default=0 value=0


I also tried to save the picture using
ffmpegin a case something is not right withopencvlike this :

ffmpeg -f v4l2 -framerate 30 -video_size 1920x1080 -i /dev/video0 -c:v libx264 -preset fast -crf 23 -t 00:01:00 output.mp4



It is saving the picture but also changing its format


[video4linux2,v4l2 @ 0x555659ed92b0] The V4L2 driver changed the video from 1920x1080 to 800x600
[video4linux2,v4l2 @ 0x555659ed92b0] The driver changed the time per frame from 1/30 to 1/15


But the format looks right when set it back to FHD using
v4l2


>>> v4l2-ctl --device=/dev/video0 --set-fmt-video=width=1920,height=1080,pixelformat=MJPG
>>> v4l2-ctl --get-fmt-video

Format Video Capture:
 Width/Height : 1920/1080
 Pixel Format : 'MJPG' (Motion-JPEG)
 Field : None
 Bytes per Line : 0
 Size Image : 4147789
 Colorspace : sRGB
 Transfer Function : Default (maps to sRGB)
 YCbCr/HSV Encoding: Default (maps to ITU-R 601)
 Quantization : Default (maps to Full Range)
 Flags :


I'm not sure what could be wrong with the format/camera and I don't think I have enough information to figure it out.


I tried to use
ffmpeginstead ofopencvand also change a few settings inopencv's cupconfig.

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