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• FFMPEG error : "First slice in a frame missing" when decoding H.265 stream

  19 octobre 2023, par Snejk

  I have a problem with decoding IP camera stream (h.265) using ffmpeg libraries.

  


  I use Live555 to receive RTP payload.

  


  mMediaSession->readSource()->getNextFrame(mVideoBuffer.data(),
mVideoBuffer.size(), Stream::Static_PayloadRead, this, Stream::Static_StreamClose, this);


  


  First two bytes (after the start code 0001) has the nal_unit_header. I am retrieving the type, from bits 1-6 ( ( NALU[0] >> 1 ) & 0x3F ). Then I am processing the data depending on the NALu type :

  


  enum NalUnitType  
{  
  NAL_UNIT_CODED_SLICE_TRAIL_N = 0,   // 0  
  NAL_UNIT_CODED_SLICE_TRAIL_R,   // 1    
  NAL_UNIT_CODED_SLICE_TSA_N,     // 2  
  NAL_UNIT_CODED_SLICE_TLA,       // 3    
  NAL_UNIT_CODED_SLICE_STSA_N,    // 4  
  NAL_UNIT_CODED_SLICE_STSA_R,    // 5    
  NAL_UNIT_CODED_SLICE_RADL_N,    // 6  
  NAL_UNIT_CODED_SLICE_DLP,       // 7     
  NAL_UNIT_CODED_SLICE_RASL_N,    // 8  
  NAL_UNIT_CODED_SLICE_TFD,       // 9   
  NAL_UNIT_RESERVED_10,  
...
  NAL_UNIT_CODED_SLICE_BLA,       // 16 
  NAL_UNIT_CODED_SLICE_BLANT,     // 17    
  NAL_UNIT_CODED_SLICE_BLA_N_LP,  // 18  
  NAL_UNIT_CODED_SLICE_IDR,       // 19  // Current name in the spec: IDR_W_DLP  
  NAL_UNIT_CODED_SLICE_IDR_N_LP,  // 20  
  NAL_UNIT_CODED_SLICE_CRA,       // 21  
  NAL_UNIT_RESERVED_22,  
 ...
  NAL_UNIT_VPS,                   // 32  
  NAL_UNIT_SPS,                   // 33  
  NAL_UNIT_PPS,                   // 34  
  NAL_UNIT_ACCESS_UNIT_DELIMITER, // 35  
  NAL_UNIT_EOS,                   // 36  
  NAL_UNIT_EOB,                   // 37  
  NAL_UNIT_FILLER_DATA,           // 38  
  NAL_UNIT_SEI,                   // 39 Prefix SEI  
  NAL_UNIT_SEI_SUFFIX,            // 40 Suffix SEI  
...
  NAL_UNIT_INVALID,  
};  


  


  If buffer doesn't have the start code, I am adding 0x00000001 at the start of the payload data, before sending it to FFmpeg. Camera is sending these NALu (in the same order) :

  


  

  1. HEVC_NAL_VPS,

  


  2. HEVC_NAL_SPS,

  


  3. HEVC_NAL_PPS,

  


  4. HEVC_NAL_IDR_W_RADL,

  


  5. HEVC_NAL_IDR_W_RADL,

  


  6. HEVC_NAL_IDR_W_RADL,

  


  7. HEVC_NAL_TRAIL_R,

  


  8. HEVC_NAL_TRAIL_R
...

  


  


  My solution works partially as I have 1/3 of image decoded. The other 2 HEVC_NAL_IDR_W_RADL slices get FFmpeg error : "First slice in a frame missing". If I lower the stream resolution I have 1/2 image with one additional HEVC_NAL_IDR_W_RADL slice.

  


  Similiar code works with H.264 stream so I know (I hope) that Live555 and FFmpeg code should be fine.

  


  Live555 doesn't reassemble the I frames (http://lists.live555.com/pipermail/live-devel/2016-September/020244.html)

  


  Is there a specific way to reassemble frame send in multiple slices. I have even tried to assemble the frame as it would be Fragmented Unit NAL type 49 (How to depacketize the fragmented frames in RTP data (over UDP) for H265/HEVC ?)

  


  Many Thanks

  


• How to resolve "ERROR : libx264 not found" ?

  13 janvier 2022, par davidvarghese

  I needed to install ffmpeg with libx264 support for enabling H.264 encoding . I installed libx264 successfully using the below script with toolchains available in android-ndk-r9d .

  



   #!/bin/bash
 NDK=~/android-ndk-r9d
 SYSROOT=$NDK/platforms/android-8/arch-arm/
 TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64
 function build_one
 {
 ./configure \
 --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
 --sysroot="$SYSROOT" \
 --host=arm-linux \
 --enable-pic \
 --enable-shared \
 --disable-cli
 make clean
 make
 make install
 }
 build_one 


  



  Now I wanted to build ffmpeg with libx264 support . I used the below script with —enable-libx264 , —enable-nonfree , —enable-gpl options as in the below script .

  



  #!/bin/bash
NDK=~/android-ndk-r9d
SYSROOT=$NDK/platforms/android-8/arch-arm/
TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86_64
function build_one
{
./configure \
--prefix=$PREFIX \
--enable-shared \
--enable-nonfree \
--enable-gpl \
--enable-libx264 \
--disable-doc \
--disable-ffmpeg \
--disable-ffplay \
--disable-ffprobe \
--disable-ffserver \
--disable-avdevice \
--disable-doc \
--disable-symver \
--cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
--target-os=linux \
--arch=arm \
--enable-cross-compile \
--sysroot=$SYSROOT \
--extra-cflags="-Os -fpic $ADDI_CFLAGS" \
--extra-ldflags="$ADDI_LDFLAGS" \
$ADDITIONAL_CONFIGURE_FLAG
make clean
make
make install
}
CPU=arm
PREFIX=$(pwd)/android/$CPU
ADDI_CFLAGS="-marm"
build_one


  



  But when I run the script I'm getting error "ERROR : libx264 not found" .

  



  I suppose ffmpeg is not able to figure out the installed location of libx264 . After libx264 installation I have libx264.so file in /usr/local/lib executable at /usr/local/bin and header files at /usr/local/include directories .

  



  What all changes do I need to make to the ffmpeg build script in-order to make it detect libx264 ?

  



  Note : I am using Ubuntu 12.04(64 bit) for cross compiling .

  


• Is it safe to ignore the error "Invalid UTF-8 in decoded subtitles text ; maybe missing -sub_charenc option Error while decoding stream" ?

  30 avril 2022, par Clogged-artery

  I was encoding a video with subtitles and I got the error, "Invalid UTF-8 in decoded subtitles text ; maybe missing -sub_charenc option. Error while decoding stream" but the video encoded anyway. What are the consequences of ignoring this error ? A google search showed a result of one guy saying it skips that sub so the resulting video will have missing subs. Can someone confirm this ?

  


  I know how to fix it but I have already converted 50+ videos with subtitles and I'm fairly certain that a few of them had this error. I just want someone to tell me that it's okay to ignore so I don't have to watch 200 hours of videos.

  


  Solution for fixing subtitle errors :

  


  Create a batch file and edit with the following :

  


  for %%a in ("*.srt") do ffmpeg -v 9 -loglevel 99 -sub_charenc CP1252 -i "%%a" "newfiles\%%~na.srt"
pause