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The Slip - Artworks
26 septembre 2011, par
Mis à jour : Septembre 2011
Langue : English
Type : Texte
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MediaSPIP 0.1 Beta version
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Participer à sa traduction
10 avril 2011Vous pouvez nous aider à améliorer les locutions utilisées dans le logiciel ou à traduire celui-ci dans n’importe qu’elle nouvelle langue permettant sa diffusion à de nouvelles communautés linguistiques.
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Sur d’autres sites (9650)
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Decoding audio via Android using FFMpeg
31 octobre 2013, par Rob HauptI can play Wav files using the below code without issues. When trying to play the exact same media in Mp3 format I only get garbled junk. I believe I am fundamentally misunderstanding how the avcodec_decode_audio3 function works.
Since the Wav file contains PCM data when it is decoded it can go straight to the AudioTrack.write function. There must be some additional step to get Mp3s to work like this. I don't know what I'm missing, but I've been pulling my hair out for a week now.
Java Code
package com.rohaupt.RRD2;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import android.app.Activity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.SystemClock;
public class player extends Activity
{
private AudioTrack track;
private FileOutputStream os;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
createEngine();
MediaPlayer mp = new MediaPlayer();
mp.start();
int bufSize = AudioTrack.getMinBufferSize(32000,
AudioFormat.CHANNEL_CONFIGURATION_STEREO,
AudioFormat.ENCODING_PCM_16BIT);
track = new AudioTrack(AudioManager.STREAM_MUSIC,
32000,
AudioFormat.CHANNEL_CONFIGURATION_STEREO,
AudioFormat.ENCODING_PCM_16BIT,
bufSize,
AudioTrack.MODE_STREAM);
byte[] bytes = new byte[bufSize];
try {
os = new FileOutputStream("/sdcard/a.out",false);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String result = loadFile("/sdcard/a.mp3",bytes);
try {
os.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
void playSound(byte[] buf, int size) {
//android.util.Log.v("ROHAUPT", "RAH Playing");
if(track.getPlayState()!=AudioTrack.PLAYSTATE_PLAYING)
track.play();
track.write(buf, 0, size);
try {
os.write(buf,0,size);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private native void createEngine();
private native String loadFile(String file, byte[] array);
/** Load jni .so on initialization*/
static {
System.loadLibrary("avutil");
System.loadLibrary("avcore");
System.loadLibrary("avcodec");
System.loadLibrary("avformat");
System.loadLibrary("avdevice");
System.loadLibrary("swscale");
System.loadLibrary("avfilter");
System.loadLibrary("ffmpeg");
}
}C Code
#include
#include
#include
#include <android></android>log.h>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#define DEBUG_TAG "ROHAUPT"
void Java_com_rohaupt_RRD2_player_createEngine(JNIEnv* env, jclass clazz)
{
avcodec_init();
av_register_all();
}
jstring Java_com_rohaupt_RRD2_player_loadFile(JNIEnv* env, jobject obj,jstring file,jbyteArray array)
{
jboolean isCopy;
int i;
int audioStream=-1;
int res;
int decoded = 0;
int out_size;
AVFormatContext *pFormatCtx;
AVCodecContext *aCodecCtx;
AVCodecContext *c= NULL;
AVCodec *aCodec;
AVPacket packet;
jclass cls = (*env)->GetObjectClass(env, obj);
jmethodID play = (*env)->GetMethodID(env, cls, "playSound", "([BI)V");//At the begining of your main function
const char * szfile = (*env)->GetStringUTFChars(env, file, &isCopy);
int16_t * pAudioBuffer = (int16_t *) av_malloc (AVCODEC_MAX_AUDIO_FRAME_SIZE*2+FF_INPUT_BUFFER_PADDING_SIZE);
int16_t * outBuffer = (int16_t *) av_malloc (AVCODEC_MAX_AUDIO_FRAME_SIZE*2+FF_INPUT_BUFFER_PADDING_SIZE);
__android_log_print(ANDROID_LOG_INFO, DEBUG_TAG, "RAH28 Starting");
res = av_open_input_file(&pFormatCtx, szfile, NULL, 0, NULL);
if(res!=0)
{
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH opening input failed with result: [%d]", res);
return file;
}
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH getting stream info");
res = av_find_stream_info(pFormatCtx);
if(res<0)
{
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH getting stream info failed with result: [%d]", res);
return file;
}
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH getting audio stream");
for(i=0; i < pFormatCtx->nb_streams; i++) {
if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO &&
audioStream < 0) {
audioStream=i;
}
}
if(audioStream==-1)
{
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH couldn't find audio stream");
return file;
}
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio stream found with result: [%d]", res);
aCodecCtx=pFormatCtx->streams[audioStream]->codec;
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio codec info loaded");
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio codec info [%d]", aCodecCtx->codec_id);
aCodec = avcodec_find_decoder(aCodecCtx->codec_id);
if(!aCodec) {
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio codec unsupported");
return file;
}
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio codec info found");
res = avcodec_open(aCodecCtx, aCodec);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio codec loaded [%d] [%d]",aCodecCtx->sample_fmt,res);
//c=avcodec_alloc_context();
av_init_packet(&packet);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH channels [%d] sample rate [%d] sample format [%d]",aCodecCtx->channels,aCodecCtx->sample_rate,aCodecCtx->sample_fmt);
int x,y;
x=0;y=0;
while (av_read_frame(pFormatCtx, &packet)>= 0) {
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH frame read: [%d] [%d]",x++,y);
if (aCodecCtx->codec_type == AVMEDIA_TYPE_AUDIO) {
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH audio ready");
int data_size = AVCODEC_MAX_AUDIO_FRAME_SIZE*2+FF_INPUT_BUFFER_PADDING_SIZE;
int size=packet.size;
y=0;
decoded = 0;
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH packet size: [%d]", size);
while(size > 0) {
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH decoding: [%d] [%d]",x,y++);
int len = avcodec_decode_audio3(aCodecCtx, pAudioBuffer, &data_size, &packet);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH 1 size [%d] len [%d] data_size [%d] out_size [%d]",size,len,data_size,out_size);
jbyte *bytes = (*env)->GetByteArrayElements(env, array, NULL);
memcpy(bytes + decoded, pAudioBuffer, len); //
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH 2");
(*env)->ReleaseByteArrayElements(env, array, bytes, 0);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH 3");
(*env)->CallVoidMethod(env, obj, play, array, len);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH 4");
size -= len;
decoded += len;
}
av_free_packet(&packet);
}
}
// Close the video file
av_close_input_file(pFormatCtx);
//__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "RAH Finished Running result: [%d]", res);
(*env)->ReleaseStringUTFChars(env, file, szfile);
return file;
}To add some detail. When Calling this function with a Wav File I get the following Log Data
I/ROHAUPT ( 227): RAH28 Starting
D/ROHAUPT ( 227): RAH getting stream info
D/ROHAUPT ( 227): RAH getting audio stream
D/ROHAUPT ( 227): RAH audio stream found with result: [0]
D/ROHAUPT ( 227): RAH audio codec info loaded
D/ROHAUPT ( 227): RAH audio codec info [65536]
D/ROHAUPT ( 227): RAH audio codec info found
D/ROHAUPT ( 227): RAH audio codec loaded [1] [0]
D/ROHAUPT ( 227): RAH channels [2] sample rate [32000] sample format [1]
D/ROHAUPT ( 227): RAH frame read: [0] [0]
D/ROHAUPT ( 227): RAH audio ready
D/ROHAUPT ( 227): RAH packet size: [4096]
D/ROHAUPT ( 227): RAH decoding: [1] [0]
D/ROHAUPT ( 227): RAH 1 size [4096] len [4096] data_size [4096] out_size [0]
D/ROHAUPT ( 227): RAH 2
D/ROHAUPT ( 227): RAH 3
D/ROHAUPT ( 227): RAH 4
D/ROHAUPT ( 227): RAH frame read: [1] [1]
D/ROHAUPT ( 227): RAH audio ready
...
D/ROHAUPT ( 227): RAH frame read: [924] [1]
D/ROHAUPT ( 227): RAH audio ready
D/ROHAUPT ( 227): RAH packet size: [4096]
D/ROHAUPT ( 227): RAH decoding: [925] [0]
D/ROHAUPT ( 227): RAH 1 size [4096] len [4096] data_size [4096] out_size [0]
D/ROHAUPT ( 227): RAH 2
D/ROHAUPT ( 227): RAH 3
D/ROHAUPT ( 227): RAH 4
D/ROHAUPT ( 227): RAH frame read: [925] [1]
D/ROHAUPT ( 227): RAH audio ready
D/ROHAUPT ( 227): RAH packet size: [3584]
D/ROHAUPT ( 227): RAH decoding: [926] [0]
D/ROHAUPT ( 227): RAH 1 size [3584] len [3584] data_size [3584] out_size [0]
D/ROHAUPT ( 227): RAH 2
D/ROHAUPT ( 227): RAH 3
D/ROHAUPT ( 227): RAH 4When calling with an Mp3 file I get the following
I/ROHAUPT ( 280): RAH28 Starting
D/ROHAUPT ( 280): RAH getting stream info
D/ROHAUPT ( 280): RAH getting audio stream
D/ROHAUPT ( 280): RAH audio stream found with result: [0]
D/ROHAUPT ( 280): RAH audio codec info loaded
D/ROHAUPT ( 280): RAH audio codec info [86017]
D/ROHAUPT ( 280): RAH audio codec info found
D/ROHAUPT ( 280): RAH audio codec loaded [1] [0]
D/ROHAUPT ( 280): RAH channels [2] sample rate [32000] sample format [1]
D/ROHAUPT ( 280): RAH frame read: [0] [0]
D/ROHAUPT ( 280): RAH audio ready
D/ROHAUPT ( 280): RAH packet size: [432]
D/ROHAUPT ( 280): RAH decoding: [1] [0]
D/ROHAUPT ( 280): RAH 1 size [432] len [432] data_size [4608] out_size [0]
D/ROHAUPT ( 280): RAH 2
...
D/ROHAUPT ( 280): RAH frame read: [822] [1]
D/ROHAUPT ( 280): RAH audio ready
D/ROHAUPT ( 280): RAH packet size: [432]
D/ROHAUPT ( 280): RAH decoding: [823] [0]
D/ROHAUPT ( 280): RAH 1 size [432] len [432] data_size [4608] out_size [0]
D/ROHAUPT ( 280): RAH 2
D/ROHAUPT ( 280): RAH 3
D/ROHAUPT ( 280): RAH 4
D/ROHAUPT ( 280): RAH frame read: [823] [1]
D/ROHAUPT ( 280): RAH audio ready
D/ROHAUPT ( 280): RAH packet size: [432]
D/ROHAUPT ( 280): RAH decoding: [824] [0]
D/ROHAUPT ( 280): RAH 1 size [432] len [432] data_size [4608] out_size [0]
D/ROHAUPT ( 280): RAH 2
D/ROHAUPT ( 280): RAH 3
D/ROHAUPT ( 280): RAH 4 -
Prevent ffmpeg from changing the intensity of colors while downscaling the resolution of the video
29 août 2022, par dravitI have a use case where I need to downscale a
716x1280mp4 video to358x640(half of the original). Command that I used is

ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" ./output.mp4


Out of 10 sample videos, 2 of the them suffered impact on colors. Below I have attached a comparison from the one which was impacted the most.




NOTE : The one on the right is a frame from the original video and the frame on the left is the one from the processed (down scaled) video. Notice the colors red and green in the image (even the skin color and hair color were changed).


What I am looking for is


- 

- Is there any way I can prevent changes like these happening ? Probably some flag on saturation, brightness, contrast or any other parameter.
- I am assuming that ffmpeg uses some default settings while downscaling a video. What made ffmpeg change colors only for these two videos ? If it made similar changes for the rest of the videos as well, how to predict this behaviour before hand ?






EDIT :


What I already have Tried ?


- 

-crfwith values 0 and 18.-preset veryslowas mentioned here






None helped


Mediainfo input V/S output







 param 

input 

output 







 color range 

Limited 

NA (attribute not in description) 




 color primaries 

BT.2020 

NA (attribute not in description) 




 transfer characteristics 

HLG 

NA (attribute not in description) 




 matrix coefficients 

BT.2020 non-constant 

NA (attribute not in description) 




 bit deapth 

8 

8 









Logs of the ffmpeg command


ffmpeg -i ./input.mp4 -vf "scale=640:640:force_original_aspect_ratio=decrease,pad=ceil(iw/2)*2:ceil(ih/2)*2" -movflags +faststart ./output.mp4
ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
 built with Apple clang version 12.0.0 (clang-1200.0.32.28)
 configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_9 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack
 libavutil 56. 51.100 / 56. 51.100
 libavcodec 58. 91.100 / 58. 91.100
 libavformat 58. 45.100 / 58. 45.100
 libavdevice 58. 10.100 / 58. 10.100
 libavfilter 7. 85.100 / 7. 85.100
 libavresample 4. 0. 0 / 4. 0. 0
 libswscale 5. 7.100 / 5. 7.100
 libswresample 3. 7.100 / 3. 7.100
 libpostproc 55. 7.100 / 55. 7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './input.mp4':
 Metadata:
 major_brand : isom
 minor_version : 512
 compatible_brands: isomiso2avc1mp41
 encoder : Lavf58.45.100
 Duration: 00:00:30.05, start: 0.000000, bitrate: 10366 kb/s
 Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt2020nc/bt2020/arib-std-b67), 716x1280, 10116 kb/s, 30 fps, 30 tbr, 19200 tbn, 38400 tbc (default)
 Metadata:
 handler_name : Core Media Video
 Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 245 kb/s (default)
 Metadata:
 handler_name : Core Media Audio
Stream mapping:
 Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
 Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7faab4808800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7faab4808800] profile High, level 3.0, 4:2:0, 8-bit
[libx264 @ 0x7faab4808800] 264 - core 161 r3027 4121277 - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to './output.mp4':
 Metadata:
 major_brand : isom
 minor_version : 512
 compatible_brands: isomiso2avc1mp41
 encoder : Lavf58.45.100
 Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 358x640, q=-1--1, 30 fps, 15360 tbn, 30 tbc (default)
 Metadata:
 handler_name : Core Media Video
 encoder : Lavc58.91.100 libx264
 Side data:
 cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
 Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
 Metadata:
 handler_name : Core Media Audio
 encoder : Lavc58.91.100 aac
[mp4 @ 0x7faab5808800] Starting second pass: moving the moov atom to the beginning of the file
frame= 901 fps=210 q=-1.0 Lsize= 3438kB time=00:00:30.02 bitrate= 938.0kbits/s speed=7.01x
video:2933kB audio:472kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.974633%
[libx264 @ 0x7faab4808800] frame I:6 Avg QP:22.60 size: 20769
[libx264 @ 0x7faab4808800] frame P:228 Avg QP:24.84 size: 7657
[libx264 @ 0x7faab4808800] frame B:667 Avg QP:27.59 size: 1697
[libx264 @ 0x7faab4808800] consecutive B-frames: 0.9% 0.9% 1.0% 97.2%
[libx264 @ 0x7faab4808800] mb I I16..4: 9.5% 64.6% 26.0%
[libx264 @ 0x7faab4808800] mb P I16..4: 2.5% 12.2% 2.5% P16..4: 37.2% 20.6% 11.2% 0.0% 0.0% skip:13.7%
[libx264 @ 0x7faab4808800] mb B I16..4: 0.4% 2.1% 0.2% B16..8: 42.2% 7.1% 1.2% direct: 1.8% skip:44.9% L0:39.4% L1:52.8% BI: 7.8%
[libx264 @ 0x7faab4808800] 8x8 transform intra:72.2% inter:74.2%
[libx264 @ 0x7faab4808800] coded y,uvDC,uvAC intra: 61.8% 67.2% 20.2% inter: 16.7% 13.9% 1.3%
[libx264 @ 0x7faab4808800] i16 v,h,dc,p: 24% 19% 7% 50%
[libx264 @ 0x7faab4808800] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 16% 15% 6% 9% 11% 7% 10% 6%
[libx264 @ 0x7faab4808800] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 16% 13% 7% 9% 10% 7% 9% 4%
[libx264 @ 0x7faab4808800] i8c dc,h,v,p: 53% 16% 26% 5%
[libx264 @ 0x7faab4808800] Weighted P-Frames: Y:3.9% UV:1.8%
[libx264 @ 0x7faab4808800] ref P L0: 57.8% 19.5% 14.8% 7.8% 0.1%
[libx264 @ 0x7faab4808800] ref B L0: 90.7% 7.2% 2.1%
[libx264 @ 0x7faab4808800] ref B L1: 95.3% 4.7%
[libx264 @ 0x7faab4808800] kb/s:799.80
[aac @ 0x7faab2036a00] Qavg: 189.523


-
Best way to diagnose VideoCapture not opening the rtmp stream
8 janvier 2021, par Greg0ryI am pulling my hair off for a few days and I'm out of ideas.


I have two rtmp streams


- 

- first stream is transcoded directly by myself (I use ffmpeg to transcode) and then I attach to that stream with opencv - VideoCapture can open the stream with no problem
- second stream is transcoded by 3rd party system (this system captures video through WebRTC and then encodes to h264) - this stream cannot be opened by VideCapture no matter what I do






I can attach with pure ffmpeg to that dodgy stream and I can restream - but this is not ideal as introduces extra network traffic and latency.


I was playing with
OPENCV_FFMPEG_CAPTURE_OPTIONSenvironmental variable (I was trying to remove audio stream, change the video codec, playing with rtmp options like thisOPENCV_FFMPEG_CAPTURE_OPTIONS="loglevel;debug" python my_script.py) - no joy

So I figured I am trying to solve this problem from wrong end. I should somehow collect underlying ffmpeg logs that should be available when calling VideoCapture. So I tried to set
OPENCV_FFMPEG_CAPTURE_OPTIONS="v;debug"but I can see no ffmpeg output when calling VideoCapture.

This is very simple python3 script I was using during tests :


import cv2 as cv
dodgy_cap = cv.VideoCapture()
dodgy_cap.open('rtmp://my_local_ip_address/rtmp/dodgy_stream_name')
print(dodgy_cap.isOpened()) # always returns False
healthy_cap = cv.VideoCapture()
healthy_cap.open('rtmp://my_local_ip_address/rtmp/healthy_stream_name')
print(healthy_cap.isOpened()) # always returns True


I collected information about both streams with ffprobe, but even though they look different I cannot see what would be the difference that prevents opencv from opening VideoCapture for dodgy stream..


This is a fragment from (very) verbose log for healthy stream :


RTMP_ClientPacket, received: notify 254 bytes 
(object begin) 
Property: 
Property: 
(object begin) 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
(object end) 
(object end) 
Metadata:
 duration 0.00
 width 2048.00
 height 1536.00
 videodatarate 0.00
 framerate 6.00
 videocodecid 7.00
 title Session streamed by "preview"
 comment h264Preview_01_main
 encoder Lavf58.20.100
 filesize 0.00

(... raw network packets ...)

Input #0, flv, from 'rtmp://my_local_ip_address/rtmp/healthy_stream_name':
 Metadata:
 title : Session streamed by "preview"
 comment : h264Preview_01_main
 encoder : Lavf58.20.100
 Duration: 00:00:00.00, start: 159.743000, bitrate: N/A
 Stream #0:0, 41, 1/1000: Video: h264 (High), 1 reference frame, yuv420p(progressive), 2048x1536, 0/1, 6 fps, 6 tbr, 1k tbn



And this is the fragment for dodgy stream :


RTMP_ClientPacket, received: notify 205 bytes 
(object begin) 
Property: 
(object begin) 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
Property: 
(object end) 
(object end) 
RTMP_ReadPacket: fd=3 

(... raw network packets ...)

Input #0, flv, from 'rtmp://my_local_ip_address/rtmp/dodgy_stream_name':
 Duration: N/A, start: 4511.449000, bitrate: N/A
 Stream #0:0, 41, 1/1000: Video: h264 (High), 1 reference frame, yuv420p(progressive, left), 640x480, 0/1, 15.17 fps, 15.08 tbr, 1k tbn, 30 tbc
 Stream #0:1, 124, 1/1000: Audio: aac (LC), 48000 Hz, mono, fltp



Both streams don't require any authentication (they are not exposed to the outside world)


Dodgy stream contains audio but I don't think it is source of problem as I was able to connect to other healthy rtmp streams that contained audio..


I have no more ideas how can I debug this problem, please help..



I found in VideoCap documentation that I can enable exception mode, however it did not help much (it says where it failed but it does not say why) :


>>> dodgy_stream = cv.VideoCapture()
>>> dodgy_stream.setExceptionMode(True)
>>> dodgy_stream.open("rtmp://my_local_ip_address/rtmp/dodgy_stream_name")
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
cv2.error: OpenCV(4.5.0) /tmp/pip-req-build-s_nildlw/opencv/modules/videoio/src/cap.cpp:177: error: (-2:Unspecified error) could not open 'rtmp://my_local_ip_address/rtmp/dodgy_stream_name' in function 'open'
</module></stdin>

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