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• Shazaam-esque music comparison [closed]

  17 janvier 2021, par Matthew Trip

  I have two files, a Full.mp4 and a Cut.mp4 I do not care about the video. I want to check if Cut appears in Full at any point. I have tried comparing the streams and their byte arrays but Rider keeps showing memory issues without an explanation. What is the general approach I should take ?

  


• ac3enc_fixed : convert to 32-bit sample format

  9 janvier 2021, par Lynne

  ac3enc_fixed : convert to 32-bit sample format
  The AC3 encoder used to be a separate library called "Aften", which
  
  got merged into libavcodec (literally, SVN commits and all).
  
  The merge preserved as much features from the library as possible.
  The code had two versions - a fixed point version and a floating
  
  point version. FFmpeg had floating point DSP code used by other
  
  codecs, the AC3 decoder including, so the floating-point DSP was
  
  simply replaced with FFmpeg's own functions.
  
  However, FFmpeg had no fixed-point audio code at that point. So
  
  the encoder brought along its own fixed-point DSP functions,
  
  including a fixed-point MDCT.
  The fixed-point MDCT itself is trivially just a float MDCT with a
  
  different type and each multiply being a fixed-point multiply.
  
  So over time, it got refactored, and the FFT used for all other codecs
  
  was templated.
  Due to design decisions at the time, the fixed-point version of the
  
  encoder operates at 16-bits of precision. Although convenient, this,
  
  even at the time, was inadequate and inefficient. The encoder is noisy,
  
  does not produce output comparable to the float encoder, and even
  
  rings at higher frequencies due to the badly approximated winow function.
  Enter MIPS (owned by Imagination Technologies at the time). They wanted
  
  quick fixed-point decoding on their FPUless cores. So they contributed
  
  patches to template the AC3 decoder so it had both a fixed-point
  
  and a floating-point version. They also did the same for the AAC decoder.
  
  They however, used 32-bit samples. Not 16-bits. And we did not have
  
  32-bit fixed-point DSP functions, including an MDCT. But instead of
  
  templating our MDCT to output 3 versions (float, 32-bit fixed and 16-bit fixed),
  
  they simply copy-pasted their own MDCT into ours, and completely
  
  ifdeffed our own MDCT code out if a 32-bit fixed point MDCT was selected.
  This is also the status quo nowadays - 2 separate MDCTs, one which
  
  produces floating point and 16-bit fixed point versions, and one
  
  sort-of integrated which produces 32-bit MDCT.
  MIPS weren't all that interested in encoding, so they left the encoder
  
  as-is, and they didn't care much about the ifdeffery, mess or quality - it's
  
  not their problem.
  So the MDCT/FFT code has always been a thorn in anyone looking to clean up
  
  code's eye.
  Backstory over. Internally AC3 operates on 25-bit fixed-point coefficients.
  
  So for the floating point version, the encoder simply runs the float MDCT,
  
  and converts the resulting coefficients to 25-bit fixed-point, as AC3 is inherently
  
  a fixed-point codec. For the fixed-point version, the input is 16-bit samples,
  
  so to maximize precision the frame samples are analyzed and the highest set
  
  bit is detected via ac3_max_msb_abs_int16(), and the coefficients are then
  
  scaled up via ac3_lshift_int16(), so the input for the FFT is always at least 14 bits,
  
  computed in normalize_samples(). After FFT, the coefficients are scaled up to 25 bits.
  This patch simply changes the encoder to accept 32-bit samples, reusing
  
  the already well-optimized 32-bit MDCT code, allowing us to clean up and drop
  
  a large part of a very messy code of ours, as well as prepare for the future lavu/tx
  
  conversion. The coefficients are simply scaled down to 25 bits during windowing,
  
  skipping 2 separate scalings, as the hacks to extend precision are simply no longer
  
  necessary. There's no point in running the MDCT always at 32 bits when you're
  
  going to drop 6 bits off anyway, the headroom is plenty, and the MDCT rounds
  
  properly.
  This also makes the encoder even slightly more accurate over the float version,
  
  as there's no coefficient conversion step necessary.
  SIZE SAVINGS :
  
  ARM32 :
  
  HARDCODED TABLES :
  
  BASE           - 10709590
  
  DROP  DSP      - 10702872 - diff :   -6.56KiB
  
  DROP  MDCT     - 10667932 - diff :  -34.12KiB - both :   -40.68KiB
  
  DROP  FFT      - 10336652 - diff : -323.52KiB - all :   -364.20KiB
  
  SOFTCODED TABLES :
  
  BASE           -  9685096
  
  DROP  DSP      -  9678378 - diff :   -6.56KiB
  
  DROP  MDCT     -  9643466 - diff :  -34.09KiB - both :   -40.65KiB
  
  DROP  FFT      -  9573918 - diff :  -67.92KiB - all :   -108.57KiB
  ARM64 :
  
  HARDCODED TABLES :
  
  BASE           - 14641112
  
  DROP  DSP      - 14633806 - diff :   -7.13KiB
  
  DROP  MDCT     - 14604812 - diff :  -28.31KiB - both :   -35.45KiB
  
  DROP  FFT      - 14286826 - diff : -310.53KiB - all :   -345.98KiB
  
  SOFTCODED TABLES :
  
  BASE           - 13636238
  
  DROP  DSP      - 13628932 - diff :   -7.13KiB
  
  DROP  MDCT     - 13599866 - diff :  -28.38KiB - both :   -35.52KiB
  
  DROP  FFT      - 13542080 - diff :  -56.43KiB - all :    -91.95KiB
  x86 :
  
  HARDCODED TABLES :
  
  BASE           - 12367336
  
  DROP  DSP      - 12354698 - diff :  -12.34KiB
  
  DROP  MDCT     - 12331024 - diff :  -23.12KiB - both :   -35.46KiB
  
  DROP  FFT      - 12029788 - diff : -294.18KiB - all :   -329.64KiB
  
  SOFTCODED TABLES :
  
  BASE           - 11358094
  
  DROP  DSP      - 11345456 - diff :  -12.34KiB
  
  DROP  MDCT     - 11321742 - diff :  -23.16KiB - both :   -35.50KiB
  
  DROP  FFT      - 11276946 - diff :  -43.75KiB - all :    -79.25KiB
  PERFORMANCE (10min random s32le) :
  
  ARM32 - before -  39.9x - 0m15.046s
  
  ARM32 - after  -  28.2x - 0m21.525s
  
                         Speed :  -30%
  ARM64 - before -  36.1x - 0m16.637s
  
  ARM64 - after  -  36.0x - 0m16.727s
  
                         Speed : -0.5%
  x86   - before - 184x -    0m3.277s
  
  x86   - after  - 190x -    0m3.187s
  
                         Speed :   +3%
  

  • [DH] doc/encoders.texi
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/ac3enc.c
  • [DH] libavcodec/ac3enc.h
  • [DH] libavcodec/ac3enc_fixed.c
  • [DH] libavcodec/ac3enc_float.c
  • [DH] libavcodec/ac3enc_template.c
  • [DH] libavcodec/version.h
  • [DH] tests/fate/ac3.mak
  • [DH] tests/fate/ffmpeg.mak
  • [DH] tests/ref/fate/unknown_layout-ac3
  • [DH] tests/ref/lavf/rm

• Invalid data stream in media could not be discarded by FFMPEG. Why is it staying and how to discard it ?

  5 décembre 2020, par Link-akro

  I have downloaded a [short media][1] i intend to convert then i will use the result as basis to practice and test any and all FFMPEG commands i learn or use later.

  


  That video seems to have an unknown invalid stream which never disappears no matter everything i tried to discard it. When i try to work with it later i get various problems like missing codec or no stream which is not the focus here but the reason why i got stubborn to remove the things i cannot deal with.

  


  The following probing prints a warning in yellow color on last row.

  


   > ffprobe -hide_banner -show_streams Movie_Countdown-youtube_I1vMKZ1kvg0.mov

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Movie_Countdown-youtube_I1vMKZ1kvg0.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2015-05-20T13:45:55.000000Z
  Duration: 00:00:10.00, start: 0.000000, bitrate: 11474 kb/s
    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 9930 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 25 tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2015-05-20T13:45:55.000000Z
      handler_name    : Apple Video Media Handler
      encoder         : H.264
      timecode        : 00:00:00:00
    Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
    Metadata:
      creation_time   : 2015-05-20T13:45:56.000000Z
      handler_name    : Apple Sound Media Handler
      timecode        : 00:00:00:00
    Stream #0:2(eng): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
    Metadata:
      creation_time   : 2015-05-20T13:46:11.000000Z
      handler_name    : Time Code Media Handler
      timecode        : 00:00:00:00
Unsupported codec with id 0 for input stream 2


  


  Below the streams output. I split the text so you see the warning without searching in the middle.

  


  [STREAM]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=Main
codec_type=video
codec_time_base=1/50
codec_tag_string=avc1
codec_tag=0x31637661
width=1920
height=1080
coded_width=1920
coded_height=1088
closed_captions=0
has_b_frames=0
sample_aspect_ratio=1:1
display_aspect_ratio=16:9
pix_fmt=yuv420p
level=40
color_range=tv
color_space=bt709
color_transfer=bt709
color_primaries=bt709
chroma_location=left
field_order=unknown
timecode=N/A
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=25/1
avg_frame_rate=25/1
time_base=1/25
start_pts=0
start_time=0.000000
duration_ts=250
duration=10.000000
bit_rate=9930739
max_bit_rate=N/A
bits_per_raw_sample=8
nb_frames=250
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
TAG:creation_time=2015-05-20T13:45:55.000000Z
TAG:language=eng
TAG:handler_name=Apple Video Media Handler
TAG:encoder=H.264
TAG:timecode=00:00:00:00
[/STREAM]
[STREAM]
index=1
codec_name=pcm_s16le
codec_long_name=PCM signed 16-bit little-endian
profile=unknown
codec_type=audio
codec_time_base=1/48000
codec_tag_string=sowt
codec_tag=0x74776f73
sample_fmt=s16
sample_rate=48000
channels=2
channel_layout=stereo
bits_per_sample=16
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=480000
duration=10.000000
bit_rate=1536000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=480000
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
TAG:creation_time=2015-05-20T13:45:56.000000Z
TAG:language=eng
TAG:handler_name=Apple Sound Media Handler
TAG:timecode=00:00:00:00
[/STREAM]
[STREAM]
index=2
codec_name=unknown
codec_long_name=unknown
profile=unknown
codec_type=data
codec_tag_string=tmcd
codec_tag=0x64636d74
id=N/A
r_frame_rate=0/0
avg_frame_rate=25/1
time_base=1/25
start_pts=0
start_time=0.000000
duration_ts=250
duration=10.000000
bit_rate=3
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=1
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
TAG:creation_time=2015-05-20T13:46:11.000000Z
TAG:language=eng
TAG:handler_name=Time Code Media Handler
TAG:timecode=00:00:00:00
[/STREAM]


  


  I scaled it down and recoded it for starters and i tried to discard the data stream with -dn and failed other methods i will mention at the end.
The output so far suggests that discarding should have worked since alternative datas are 0kB and no stream 2 is listed.

  


   > ffmpeg -hide_banner -dn -i C:\Users\admin-dix\Downloads\Movie_Countdown-youtube_I1vMKZ1kvg0.mov -vf "scale=h=450:w=800" -f mp4 -c:a aac -c:v libx264 mov_countdown.mp4

Output #0, mp4, to 'mov_countdown.mp4':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    encoder         : Lavf58.45.100
    Stream #0:0(eng): Video: h264 (libx264) (avc1 / 0x31637661), yuv420p(progressive), 800x450 [SAR 1:1 DAR 16:9], q=-1--1, 0.04 fps, 12800 tbn, 25 tbc (default)
    Metadata:
      creation_time   : 2015-05-20T13:45:55.000000Z
      handler_name    : Apple Video Media Handler
      timecode        : 00:00:00:00
      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(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      creation_time   : 2015-05-20T13:45:56.000000Z
      handler_name    : Apple Sound Media Handler
      timecode        : 00:00:00:00
      encoder         : Lavc58.91.100 aac
frame=  250 fps= 43 q=-1.0 Lsize=     342kB time=00:00:10.00 bitrate= 280.1kbits/s speed= 1.7x
video:175kB audio:159kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.710857%


  


  Then ffprobe disagrees, there is still the stream and the warning.

  


  ffprobe mov_countdown.mp4

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'mov_countdown.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:10.02, start: 0.000000, bitrate: 279 kb/s
    Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 800x450 [SAR 1:1 DAR 16:9], 142 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : Apple Video Media Handler
      timecode        : 00:00:00:00
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 129 kb/s (default)
    Metadata:
      handler_name    : Apple Sound Media Handler
    Stream #0:2(eng): Data: none (tmcd / 0x64636D74), 0 kb/s
    Metadata:
      handler_name    : Apple Video Media Handler
      timecode        : 00:00:00:00
Unsupported codec with id 0 for input stream 2


  


  I tried negative mapping as per this answer -map 0:d which failed. I did not understand -discard option as ffmpeg documentation refers to from the -vn,-an,-dn entries as it does not specify a stream.

  


  Why does it do that and how can i remove that stream i do not know and do not want to care about in future tests ?

  


  [1] : Clean Retro Movie Countdown - YouTube from Philippe Moesch https://www.youtube.com/watch?v=I1vMKZ1kvg0