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• Android : mp4 file plays when downloaded but when choosing "Video" player gets "Cannot play video"

  11 juillet 2019, par gview

  I’ve converted the video to an mp4 with ffmpeg using the h264 codec and AAC, and used the baseline profile.

  Videos are 540x360x250kbps

  I then ran qt-faststart on the file to move the atoms into the right order.

  I’ve stuck the file up on a wiki we use and created a link to it.

  My test phone is a Samsung Galaxy S3.

  When I browse to the page that has links to the mp4’s on it, and I click on them, I get a popup window with 2 options : Internet and Video.

  If I download the videos using the "Internet" option, I can play them on the phone without issue.

  I’ve done other encodings with the main profile as well, and these also play fine. I thought that a powerful phone like the s3 would be able to handle the more advanced compression schemes available in h264, however I’ve also browsed the Android docs in regards to supported video formats, and it seems to state that only the "baseline" compression profile is supported.

  Regardless, what doesn’t work is trying to use the "Video" option which I assume tries to stream the video.

  For the wiki in question, clicking on the link reveals that the content-type and content-length headers are being set :

  Content-Length  6175996
  
  Content-Type    video/mp4;charset=UTF-8

  Clicking on the link with a browser invokes a player (Quicktime in most cases) that can play the mp4’s.

  Is there more to having the file HTTP streamable beyond making a link to it ? Why won’t my Android 4 play these files ?

  UPDATE :
  I decided to make a quick HTML5 page using the video tag, and the videos do play on both my Galaxy S3 and the latest IOS.

• Edit H264 video stream header information ("start_pts" and "start_time")

  27 juin 2020, par David

  I have a video clip that appears to be slightly corrupted. Does not play on VLC but works on Potplayer. I used FFprobe to get information on the video.

  


  The problem appears to be with the start points of the video stream :

  


  time_base=1/90000
start_pts=585050940
start_time=6500.566000
duration_ts=585050940
duration=6500.566000
bit_rate=3123218


  


  I'm just wondering whether it is possible to manually edit the "start_pts" and "start_time" to 0 ? Is there any specific software to do this ? Due to large size of video file, I couldn't load it in Notepad++.

  


  Full ffprobe output shown below :

  


  # ffprobe output

[streams.stream.0]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=unknown
codec_type=video
codec_time_base=1/60
codec_tag_string=avc1
codec_tag=0x31637661
width=1920
height=1080
coded_width=1920
coded_height=1080
closed_captions=0
has_b_frames=0
sample_aspect_ratio=N/A
display_aspect_ratio=N/A
pix_fmt=unknown
level=-99
color_range=unknown
color_space=unknown
color_transfer=unknown
color_primaries=unknown
chroma_location=unspecified
field_order=unknown
timecode=N/A
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=30/1
avg_frame_rate=30/1
time_base=1/90000
start_pts=585050940
start_time=6500.566000
duration_ts=585050940
duration=6500.566000
bit_rate=3123218
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=195017
nb_read_frames=N/A
nb_read_packets=N/A

[streams.stream.0.disposition]
default=1
dub=0
original=0
comment=0
lyrics=0
karaoke=0
forced=0
hearing_impaired=0
visual_impaired=0
clean_effects=0
attached_pic=0
timed_thumbnails=0

[streams.stream.0.tags]
language=und
handler_name=VideoHandler

[streams.stream.1]
index=1
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=LC
codec_type=audio
codec_time_base=1/48000
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=fltp
sample_rate=48000
channels=2
channel_layout=stereo
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/48000
start_pts=0
start_time=0.000000
duration_ts=312029184
duration=6500.608000
bit_rate=189376
max_bit_rate=189376
bits_per_raw_sample=N/A
nb_frames=304718
nb_read_frames=N/A
nb_read_packets=N/A

[streams.stream.1.disposition]
default=1
dub=0
original=0
comment=0
lyrics=0
karaoke=0
forced=0
hearing_impaired=0
visual_impaired=0
clean_effects=0
attached_pic=0
timed_thumbnails=0

[streams.stream.1.tags]
language=eng
handler_name=SoundHandler

[format]
filename=D\:\\Start\\test.mp4
nb_streams=2
nb_programs=0
format_name=mov,mp4,m4a,3gp,3g2,mj2
format_long_name=QuickTime / MOV
start_time=0.000000
duration=6500.608000
size=2703218140
bit_rate=3326726
probe_score=100

[format.tags]
major_brand=isom
minor_version=512
compatible_brands=isomiso2avc1mp41


  


• Slow FPS with OpenCV C++ RaspberryPi

  23 février 2021, par aquamoon

  I have written a simple C++ program using OpenCV to test fps on raspberry pi.

  


  #include <iostream>&#xA;#include <chrono>&#xA;#include <thread>&#xA;#include &#xA;#include <string>&#xA;&#xA;#include <opencv2></opencv2>opencv.hpp>&#xA;#include <opencv2></opencv2>tracking.hpp>&#xA;#include <opencv2></opencv2>core/ocl.hpp>&#xA;&#xA;using namespace cv;&#xA;using namespace std;&#xA;using namespace std::chrono;&#xA;using namespace std::this_thread;&#xA;using namespace cv::ml;&#xA;&#xA;int main(void) &#xA;{&#xA;    VideoCapture camera(0); &#xA;    camera.set(CAP_PROP_FRAME_WIDTH, 640);&#xA;    camera.set(CAP_PROP_FRAME_HEIGHT, 480);&#xA;    camera.set(CAP_PROP_FPS, 25);&#xA;    &#xA;    Mat frame;&#xA;    while (camera.read(frame)) {&#xA;        for (size_t i = 0; i &lt; frame.dataend - frame.datastart; i&#x2B;&#x2B;)&#xA;            std::cout &lt;&lt; frame.data[i];&#xA;    }&#xA;}&#xA;</string></thread></chrono></iostream>

  


  I then use the following scrips to test fps.
The first uses raspvid as the input, the second used my C++ program as input
The raspvid version gets to the 25fps.
My C++ program never goes over 10fps.
Any ide why this is ?

  


  raspivid -w 640 -h 480 -fps 25 -t 120000 -o -| ffmpeg -re -i pipe:0 -y -an -c:v copy -f null /dev/null


  


  and

  


  ./PiImageAnalyzer.out | ffmpeg -re -f rawvideo -pixel_format bgr24 -video_size 640x480 -framerate 25 -i pipe:0 -y -an -c:v copy -f null /dev/null


  


  Update

  


  these scripts can also be used

  


  raspivid -w 640 -h 480 -fps 25 -t 120000 -o -| ffplay -i -


  


  and

  


  ./PiImageAnalyzer.out | ffplay -f rawvideo -pixel_format bgr24 -video_size 640x480 -framerate 25 -i -