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• How to create a video out of frames without saving it to disk using python ?

  6 septembre 2022, par brenodacosta

  I have a function that returns a frame as result. I wanted to know how to make a video out of a for-loop with this function without saving every frame and then creating the video.

  


  What I have from now is something similar to :

  


  import cv2
out = cv2.VideoWriter('video.mp4',cv2.VideoWriter_fourcc(*'DIVX'), 14.25,(500,258))
for frame in frames:
    img_result = MyImageTreatmentFunction(frame) # returns a numpy array image
    out.write(img_result)
out.release()


  


  Then the video will be created as video.mp4 and I can access it on memory. I'm asking myself if there's a way to have this video in a variable that I can easily convert to bytes later. My purpose for that is to send the video via HTTP post.

  


  I've looked on ffmpeg-python and opencv but I didn't find anything that applies to my case.

  


• Issues Streaming FLV Video from RTSP using FFmpeg and Python to flv.js

  14 juin 2024, par yternal

  I am currently working on a project where I need to stream video from an RTSP source, convert it to FLV format using FFmpeg, and then send the FLV stream to clients upon request. The code I have written to achieve this is as follows :

  


  import subprocess
from flask import Flask, Response, stream_with_context

app = Flask(__name__)

flv_header = b''

def update_stream(ffmpeg_path="ffmpeg", rtsp_url='rtsp://192.168.1.168/0', rtsp_id="rtsp01"):
    global flv_header

    command = [
        ffmpeg_path,
        '-i', rtsp_url,
        '-c:v', 'libx264',
        '-c:a', 'aac',
        '-b:v', '1M',
        '-g', '30',
        '-preset', 'ultrafast',
        '-bsf:v', 'dump_extra',
        '-f', 'flv',
        '-'
    ]
    process = subprocess.Popen(
        command,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE
    )
    flv_header = process.stdout.read(1024)
    while True:
        data = process.stdout.read(1024)
        if not data:
            break
        producer.notify(rtsp_id, data)

@app.route('/flv//')
def flv_stream(user_id, rtsp_id):
    try:
        consumer_queue = producer.register(user_id, rtsp_id)

        @stream_with_context
        def generate():
            yield flv_header
            while True:
                yield consumer_queue.get()

        response = Response(generate(), mimetype='video/x-flv')
        response.headers.add('Access-Control-Allow-Origin', '*')  # Allow all origins
        response.headers.add('Access-Control-Allow-Methods', '*')  # Allow all HTTP methods
        response.headers.add('Access-Control-Allow-Headers', 'Content-Type')  # Allow specific headers
        return response
    except Exception as e:
        print(f'{e}')


  


  In order to handle initial playback issues in FFplay and VLC, I save the first 1024 bytes of the FLV stream and send this header before streaming the actual data. This workaround allows playback in FFplay and VLC, but it does not work with flv.js.

  


  When attempting to play the stream using flv.js, the stream keeps loading indefinitely, and the console outputs warnings like :

  


  flv.min.js:9 [FLVDemuxer] > Invalid PrevTagSize 3491417133
[FLVDemuxer] > Unsupported tag type 204, skipped


  


  I have tried several modifications to the FFmpeg command, including adding parameters such as -bsf:v dump_extra, but none of these changes have resolved the issue. My expectation is that the FLV stream would play smoothly in flv.js just as it does in FFplay and VLC.

  


• Revision 3c5256d572 : VP9_LPF_VERTICAL_16_DUAL_SSE2 optimization The vp9_lpf_vertical_16_dual functio

  29 avril 2015, par levytamar82

  Changed Paths :
   Modify /vp9/common/x86/vp9_loopfilter_intrin_sse2.c

  
  
  VP9_LPF_VERTICAL_16_DUAL_SSE2 optimization

  The vp9_lpf_vertical_16_dual function optimized for x86 32bit target. The hot
  code in that function was caused by the call to the transpose8x16.
  The gcc generated assembly created uneeded fills and spills to the stack. By
  interleaving 2 loads and unpack instructions, in addition to hoisting the
  consumer
  instruction closer to the producer instructions, we eliminated most of the fills
  and spills and improve the function-level performance by 17%.
  credit for writing the function as well as finding the root cause goes to Erik
  Niemeyer (erik.a.niemeyer@intel.com)

  Change-Id : I6173cf53956d52918a047d1c53d9a673f952ec46