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• How to use ffmpeg-python library to download a Twitch VOD with a link retrieved using the streamlink library

  28 octobre 2020, par Daniel Norfolk

  This is the whole code, for easy reference :

  


  import urllib.request
import streamlink
import ffmpeg
stream_url = streamlink.streams("https://www.twitch.tv/videos/783301562")['best'].url
print(stream_url)

try:
    urllib.request.urlretrieve(stream_url, "vod.m3u8")
except Exception as e:
    print(e)

stream = (
    ffmpeg
    .input('vod.m3u8')
    .output('output.mp4')
    .run
)
print(stream)


  


  I am looking at a way of downloading Twitch VODs. I started with the link to a VOD : https://www.twitch.tv/videos/783301562 . I then used the code :

  


  stream_url = streamlink.streams("https://www.twitch.tv/videos/783301562")['best'].url
print(stream_url)


  


  This gave me a new link which, when I go to this link it downloaded a file with a '.m3u8' extension. This link is : https://dqrpb9wgowsf5.cloudfront.net/ab3654a5992fbfa52ccb_briziana_40240109614_1603789265/chunked/index-dvr.m3u8

  


  From here, I first tried to put the link directly into the following code :

  


  stream = (
    ffmpeg
    .input(stream_url)
    .output('output.mp4')
    .run
)
print(stream)


  


  This didn't output any mp4 file but did give the output :

  


  


  >

  


  


  I then added the following code to download the file, I also change the ffmpeg code to use the downloaded file rather then the url :

  


  try:
    urllib.request.urlretrieve(stream_url, "vod.m3u8")
except Exception as e:
    print(e)

stream = (
    ffmpeg
    .input('vod.m3u8')
    .output('output.mp4')
    .run
)
print(stream)


  


  This gave the same result, no mp4 file with the same output as above. Any help would be greatly appreciated !

  


• vulkan : add support for regular descriptor pools

  22 septembre 2024, par Lynne

  vulkan : add support for regular descriptor pools
  This permits :
  
   - The use of Vulkan filtering on many more devices
  
   - Better debugging due to lack of descriptor buffer support in layers
  Much of the changes here are due to a requirement that updates to
  
  descriptors must happen between the command buffer being waited on,
  
  and the pipeline not being bound.
  We routinely did it the other way around, by updating only after
  
  we bind the pipeline.
  

  • [DH] libavfilter/vf_gblur_vulkan.c
  • [DH] libavfilter/vf_nlmeans_vulkan.c
  • [DH] libavfilter/vulkan_filter.c
  • [DH] libavutil/hwcontext_vulkan.c
  • [DH] libavutil/vulkan.c
  • [DH] libavutil/vulkan.h
  • [DH] libavutil/vulkan_functions.h

• avfilter/af_stereowiden : fix read/write past the end of buffer

  12 juillet 2016, par Alexey Tourbin

  avfilter/af_stereowiden : fix read/write past the end of buffer
  The stereowiden filter uses a buffer, s->buffer[], and a pointer
  
  within the buffer, s->write, to implement inter-channel delays.
  
  The loop which applies the delayed samples turns out to be faulty.
     109      for (n = 0 ; n < in->nb_samples ; n++, src += 2, dst += 2) 
  
     110          const float left = src[0], right = src[1] ;
  
     111          float *read = s->write + 2 ;
  
     112
  
     113          if (read > s->buffer + s->length)
  
     114              read = s->buffer ;
  
     115
  
     116          dst[0] = drymix * left - crossfeed * right - feedback * read[1] ;
  
     117          dst[1] = drymix * right - crossfeed * left - feedback * read[0] ;
  
     118
  
     119          s->write[0] = left ;
  
     120          s->write[1] = right ;
  
     121
  
     122          if (s->write == s->buffer + s->length)
  
     123              s->write = s->buffer ;
  
     124          else
  
     125              s->write += 2 ;
  
     126      
  For one, the buffer gets written past its end in lines 119-120, before
  
  the bound check is done in lines 122-123.  This can be easily confirmed
  
  by valgrind.
  ==3544== Invalid read of size 4
  
  ==3544==    at 0x593B41 : filter_frame (af_stereowiden.c:116)
  
  ==3544==  Address 0xb1b03c4 is 4 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid read of size 4
  
  ==3544==    at 0x593B66 : filter_frame (af_stereowiden.c:117)
  
  ==3544==  Address 0xb1b03c0 is 0 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid write of size 4
  
  ==3544==    at 0x593B79 : filter_frame (af_stereowiden.c:119)
  
  ==3544==  Address 0xb1b03c0 is 0 bytes after a block of size 7,680 alloc’d
  
  ==3544==
  
  ==3544== Invalid write of size 4
  
  ==3544==    at 0x593B7D : filter_frame (af_stereowiden.c:120)
  
  ==3544==  Address 0xb1b03c4 is 4 bytes after a block of size 7,680 alloc’d
  Also, using two separate pointers, s->write and read = s->write + 2,
  
  does not seem to be well thought out.  To apply the delay of s->buffer[],
  
  it is enough to read the delayed samples at the current position within
  
  the buffer, and then to store new samples at the same current position.
  
  Thus the application of delayed samples can probably be best described
  
  with a single pointer s->cur.
  I also introduce a minor change to ensure that the size of s->buffer[]
  
  is always a multiple of 2.  Since the delay parameter is a float, it is
  
  otherwise possible to trick the code into allocating off-by-one buffer.
  

  • [DH] libavfilter/af_stereowiden.c