ffmpeg filter_complex en hosting compartido donde el subproceso es limitado

(Descargo de responsabilidad: soy bueno en PHP, pero no estoy familiarizado con ffmpeg o líneas de comando en general, por lo que todo mi código se copia de Internet)

Estoy usando un alojamiento compartido con ffmpeg habilitado (versión 2.6.8).

Para que los comandos ffmpeg funcionen, necesito agregarlos -threads 1al comando. Todo funcionó bien hasta el punto que necesitaba para el usuario filter_complex.

Por ejemplo, este comando:

ffmpeg -y -i "audio_1.mp3" -i "audio_2.mp3" -threads 1 -filter_complex "[0:a][1:a]amerge=inputs=2[a]" -map [a] -c:a libfdk_aac "test5.mp3" 2>&1

... debería superponer dos archivos MP3, pero da como resultado esta salida:

Array (
    [0] => ffmpeg version 2.6.8 Copyright (c) 2000-2016 the FFmpeg developers
    [1] =>   built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-16)
    [2] =>   configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-gnutls --enable-ladspa --enable-libass --enable-libdc1394 --enable-libfaac --enable-nonfree --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libx264 --enable-libx265 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 --enable-runtime-cpudetect
    [3] =>   libavutil      54. 20.100 / 54. 20.100
    [4] =>   libavcodec     56. 26.100 / 56. 26.100
    [5] =>   libavformat    56. 25.101 / 56. 25.101
    [6] =>   libavdevice    56.  4.100 / 56.  4.100
    [7] =>   libavfilter     5. 11.102 /  5. 11.102
    [8] =>   libavresample   2.  1.  0 /  2.  1.  0
    [9] =>   libswscale      3.  1.101 /  3.  1.101
    [10] =>   libswresample   1.  1.100 /  1.  1.100
    [11] =>   libpostproc    53.  3.100 / 53.  3.100
    [12] => Input #0, mp3, from 'audio_1.mp3':
    [13] =>   Metadata:
    [14] =>     encoder         : Lavf54.21.100
    [15] =>   Duration: 00:00:04.10, start: 0.023021, bitrate: 64 kb/s
    [16] =>     Stream #0:0: Audio: mp3, 48000 Hz, mono, s16p, 64 kb/s
    [17] => Input #1, mp3, from 'audio_2.mp3':
    [18] =>   Metadata:
    [19] =>     encoder         : Lavf54.21.100
    [20] =>   Duration: 00:00:10.25, start: 0.023021, bitrate: 64 kb/s
    [21] =>     Stream #1:0: Audio: mp3, 48000 Hz, mono, s16p, 64 kb/s
    [22] => [AVFilterGraph @ 0x21748a0] Error initializing threading.
    [23] => [AVFilterGraph @ 0x21748a0] Error creating filter 'amerge'
    [24] => Error configuring filters.
)

Encontré pequeñas cantidades de información en línea sobre -filter_threads 1e -filter_complex_threads 1intenté insertarlas en varios lugares en el comando: el error siempre es

Unrecognized option 'filter_threads'.
Error splitting the argument list: Option not found

o

Unrecognized option 'filter_complex_threads'.
Error splitting the argument list: Option not found

Hablé con el soporte del host y me dijeron que el comando debe estar equivocado, pero que todo lo que intento filter_complexfalla debido al subproceso.

Mi lista de filtros ( ffmpeg -filters) muestra:

Array
(
    [0] => Filters:
    [1] =>   T.. = Timeline support
    [2] =>   .S. = Slice threading
    [3] =>   ..C = Commmand support
    [4] =>   A = Audio input/output
    [5] =>   V = Video input/output
    [6] =>   N = Dynamic number and/or type of input/output
    [7] =>   | = Source or sink filter
    [8] =>  T.. adelay           A->A       Delay one or more audio channels.
    [9] =>  ... aecho            A->A       Add echoing to the audio.
    [10] =>  ... aeval            A->A       Filter audio signal according to a specified expression.
    [11] =>  T.. afade            A->A       Fade in/out input audio.
    [12] =>  ... aformat          A->A       Convert the input audio to one of the specified formats.
    [13] =>  ... ainterleave      N->A       Temporally interleave audio inputs.
    [14] =>  ... allpass          A->A       Apply a two-pole all-pass filter.
    [15] =>  ... amerge           N->A       Merge two or more audio streams into a single multi-channel stream.
    [16] =>  ... amix             N->A       Audio mixing.
    [17] =>  ... anull            A->A       Pass the source unchanged to the output.
    [18] =>  T.. apad             A->A       Pad audio with silence.
    [19] =>  ... aperms           A->A       Set permissions for the output audio frame.
    [20] =>  ... aphaser          A->A       Add a phasing effect to the audio.
    [21] =>  ... aresample        A->A       Resample audio data.
    [22] =>  ... aselect          A->N       Select audio frames to pass in output.
    [23] =>  ... asendcmd         A->A       Send commands to filters.
    [24] =>  ... asetnsamples     A->A       Set the number of samples for each output audio frames.
    [25] =>  ... asetpts          A->A       Set PTS for the output audio frame.
    [26] =>  ... asetrate         A->A       Change the sample rate without altering the data.
    [27] =>  ... asettb           A->A       Set timebase for the audio output link.
    [28] =>  ... ashowinfo        A->A       Show textual information for each audio frame.
    [29] =>  ... asplit           A->N       Pass on the audio input to N audio outputs.
    [30] =>  ... astats           A->A       Show time domain statistics about audio frames.
    [31] =>  ... astreamsync      AA->AA     Copy two streams of audio data in a configurable order.
    [32] =>  ... asyncts          A->A       Sync audio data to timestamps
    [33] =>  ..C atempo           A->A       Adjust audio tempo.
    [34] =>  ... atrim            A->A       Pick one continuous section from the input, drop the rest.
    [35] =>  ... bandpass         A->A       Apply a two-pole Butterworth band-pass filter.
    [36] =>  ... bandreject       A->A       Apply a two-pole Butterworth band-reject filter.
    [37] =>  ... bass             A->A       Boost or cut lower frequencies.
    [38] =>  ... biquad           A->A       Apply a biquad IIR filter with the given coefficients.
    [39] =>  ... channelmap       A->A       Remap audio channels.
    [40] =>  ... channelsplit     A->N       Split audio into per-channel streams.
    [41] =>  ... compand          A->A       Compress or expand audio dynamic range.
    [42] =>  T.. dcshift          A->A       Apply a DC shift to the audio.
    [43] =>  ... earwax           A->A       Widen the stereo image.
    [44] =>  ... ebur128          A->N       EBU R128 scanner.
    [45] =>  ... equalizer        A->A       Apply two-pole peaking equalization (EQ) filter.
    [46] =>  ... flanger          A->A       Apply a flanging effect to the audio.
    [47] =>  ... highpass         A->A       Apply a high-pass filter with 3dB point frequency.
    [48] =>  ... join             N->A       Join multiple audio streams into multi-channel output.
    [49] =>  ..C ladspa           N->A       Apply LADSPA effect.
    [50] =>  ... lowpass          A->A       Apply a low-pass filter with 3dB point frequency.
    [51] =>  ... pan              A->A       Remix channels with coefficients (panning).
    [52] =>  ... replaygain       A->A       ReplayGain scanner.
    [53] =>  ... resample         A->A       Audio resampling and conversion.
    [54] =>  ... silencedetect    A->A       Detect silence.
    [55] =>  ... silenceremove    A->A       Remove silence.
    [56] =>  ... treble           A->A       Boost or cut upper frequencies.
    [57] =>  T.C volume           A->A       Change input volume.
    [58] =>  ... volumedetect     A->A       Detect audio volume.
    [59] =>  ... aevalsrc         |->A       Generate an audio signal generated by an expression.
    [60] =>  ... anullsrc         |->A       Null audio source, return empty audio frames.
    [61] =>  ... sine             |->A       Generate sine wave audio signal.
    [62] =>  ... anullsink        A->|       Do absolutely nothing with the input audio.
    [63] =>  ... alphaextract     V->N       Extract an alpha channel as a grayscale image component.
    [64] =>  ... alphamerge       VV->V      Copy the luma value of the second input into the alpha channel of the first input.
    [65] =>  ... ass              V->V       Render ASS subtitles onto input video using the libass library.
    [66] =>  T.. bbox             V->V       Compute bounding box for each frame.
    [67] =>  ... blackdetect      V->V       Detect video intervals that are (almost) black.
    [68] =>  ... blackframe       V->V       Detect frames that are (almost) black.
    [69] =>  TS. blend            VV->V      Blend two video frames into each other.
    [70] =>  T.. boxblur          V->V       Blur the input.
    [71] =>  T.. codecview        V->V       Visualize information about some codecs
    [72] =>  T.. colorbalance     V->V       Adjust the color balance.
    [73] =>  T.. colorchannelmixer V->V       Adjust colors by mixing color channels.
    [74] =>  T.. colorlevels      V->V       Adjust the color levels.
    [75] =>  T.. colormatrix      V->V       Convert color matrix.
    [76] =>  ... copy             V->V       Copy the input video unchanged to the output.
    [77] =>  ... crop             V->V       Crop the input video.
    [78] =>  T.. cropdetect       V->V       Auto-detect crop size.
    [79] =>  TS. curves           V->V       Adjust components curves.
    [80] =>  TS. dctdnoiz         V->V       Denoise frames using 2D DCT.
    [81] =>  ... decimate         N->V       Decimate frames (post field matching filter).
    [82] =>  ... dejudder         V->V       Remove judder produced by pullup.
    [83] =>  T.. delogo           V->V       Remove logo from input video.
    [84] =>  ... deshake          V->V       Stabilize shaky video.
    [85] =>  T.. drawbox          V->V       Draw a colored box on the input video.
    [86] =>  T.. drawgrid         V->V       Draw a colored grid on the input video.
    [87] =>  T.C drawtext         V->V       Draw text on top of video frames using libfreetype library.
    [88] =>  T.. edgedetect       V->V       Detect and draw edge.
    [89] =>  ... elbg             V->V       Apply posterize effect, using the ELBG algorithm.
    [90] =>  ..C eq               V->V       Adjust brightness, contrast, gamma, and saturation.
    [91] =>  ... extractplanes    V->N       Extract planes as grayscale frames.
    [92] =>  .S. fade             V->V       Fade in/out input video.
    [93] =>  ... field            V->V       Extract a field from the input video.
    [94] =>  ... fieldmatch       N->V       Field matching for inverse telecine.
    [95] =>  T.. fieldorder       V->V       Set the field order.
    [96] =>  ... format           V->V       Convert the input video to one of the specified pixel formats.
    [97] =>  ... fps              V->V       Force constant framerate.
    [98] =>  ... framepack        VV->V      Generate a frame packed stereoscopic video.
    [99] =>  T.. framestep        V->V       Select one frame every N frames.
    [100] =>  T.. fspp             V->V       Apply Fast Simple Post-processing filter.
    [101] =>  T.. geq              V->V       Apply generic equation to each pixel.
    [102] =>  T.. gradfun          V->V       Debands video quickly using gradients.
    [103] =>  TS. haldclut         VV->V      Adjust colors using a Hald CLUT.
    [104] =>  .S. hflip            V->V       Horizontally flip the input video.
    [105] =>  T.. histeq           V->V       Apply global color histogram equalization.
    [106] =>  ... histogram        V->V       Compute and draw a histogram.
    [107] =>  T.. hqdn3d           V->V       Apply a High Quality 3D Denoiser.
    [108] =>  .S. hqx              V->V       Scale the input by 2, 3 or 4 using the hq*x magnification algorithm.
    [109] =>  T.C hue              V->V       Adjust the hue and saturation of the input video.
    [110] =>  ... idet             V->V       Interlace detect Filter.
    [111] =>  T.. il               V->V       Deinterleave or interleave fields.
    [112] =>  ... interlace        V->V       Convert progressive video into interlaced.
    [113] =>  ... interleave       N->V       Temporally interleave video inputs.
    [114] =>  ... kerndeint        V->V       Apply kernel deinterlacing to the input.
    [115] =>  .S. lenscorrection   V->V       Rectify the image by correcting for lens distortion.
    [116] =>  TS. lut3d            V->V       Adjust colors using a 3D LUT.
    [117] =>  T.. lut              V->V       Compute and apply a lookup table to the RGB/YUV input video.
    [118] =>  T.. lutrgb           V->V       Compute and apply a lookup table to the RGB input video.
    [119] =>  T.. lutyuv           V->V       Compute and apply a lookup table to the YUV input video.
    [120] =>  ... mcdeint          V->V       Apply motion compensating deinterlacing.
    [121] =>  ... mergeplanes      N->V       Merge planes.
    [122] =>  ... mpdecimate       V->V       Remove near-duplicate frames.
    [123] =>  T.. negate           V->V       Negate input video.
    [124] =>  ... noformat         V->V       Force libavfilter not to use any of the specified pixel formats for the input to the next filter.
    [125] =>  TS. noise            V->V       Add noise.
    [126] =>  ... null             V->V       Pass the source unchanged to the output.
    [127] =>  T.C overlay          VV->V      Overlay a video source on top of the input.
    [128] =>  T.. owdenoise        V->V       Denoise using wavelets.
    [129] =>  ... pad              V->V       Pad the input video.
    [130] =>  ... palettegen       V->V       Find the optimal palette for a given stream.
    [131] =>  ... paletteuse       VV->V      Use a palette to downsample an input video stream.
    [132] =>  ... perms            V->V       Set permissions for the output video frame.
    [133] =>  TS. perspective      V->V       Correct the perspective of video.
    [134] =>  T.. phase            V->V       Phase shift fields.
    [135] =>  ... pixdesctest      V->V       Test pixel format definitions.
    [136] =>  T.C pp               V->V       Filter video using libpostproc.
    [137] =>  T.. pp7              V->V       Apply Postprocessing 7 filter.
    [138] =>  ... psnr             VV->V      Calculate the PSNR between two video streams.
    [139] =>  ... pullup           V->V       Pullup from field sequence to frames.
    [140] =>  T.. qp               V->V       Change video quantization parameters.
    [141] =>  T.. removelogo       V->V       Remove a TV logo based on a mask image.
    [142] =>  ... repeatfields     V->V       Hard repeat fields based on MPEG repeat field flag.
    [143] =>  TSC rotate           V->V       Rotate the input image.
    [144] =>  T.. sab              V->V       Apply shape adaptive blur.
    [145] =>  ... scale            V->V       Scale the input video size and/or convert the image format.
    [146] =>  ... select           V->N       Select video frames to pass in output.
    [147] =>  ... sendcmd          V->V       Send commands to filters.
    [148] =>  ... separatefields   V->V       Split input video frames into fields.
    [149] =>  ... setdar           V->V       Set the frame display aspect ratio.
    [150] =>  ... setfield         V->V       Force field for the output video frame.
    [151] =>  ... setpts           V->V       Set PTS for the output video frame.
    [152] =>  ... setsar           V->V       Set the pixel sample aspect ratio.
    [153] =>  ... settb            V->V       Set timebase for the video output link.
    [154] =>  ... showinfo         V->V       Show textual information for each video frame.
    [155] =>  T.. showpalette      V->V       Display frame palette
    [156] =>  ... shuffleplanes    V->V       Shuffle video planes
    [157] =>  .S. signalstats      V->V       Generate statistics from video analysis.
    [158] =>  T.. smartblur        V->V       Blur the input video without impacting the outlines.
    [159] =>  ... split            V->N       Pass on the input to N video outputs.
    [160] =>  T.C spp              V->V       Apply a simple post processing filter.
    [161] =>  ... stereo3d         V->V       Convert video stereoscopic 3D view.
    [162] =>  ... subtitles        V->V       Render text subtitles onto input video using the libass library.
    [163] =>  ... super2xsai       V->V       Scale the input by 2x using the Super2xSaI pixel art algorithm.
    [164] =>  ... swapuv           V->V       Swap U and V components.
    [165] =>  .S. tblend           V->V       Blend successive frames.
    [166] =>  ... telecine         V->V       Apply a telecine pattern.
    [167] =>  ... thumbnail        V->V       Select the most representative frame in a given sequence of consecutive frames.
    [168] =>  ... tile             V->V       Tile several successive frames together.
    [169] =>  ... tinterlace       V->V       Perform temporal field interlacing.
    [170] =>  .S. transpose        V->V       Transpose input video.
    [171] =>  ... trim             V->V       Pick one continuous section from the input, drop the rest.
    [172] =>  T.. unsharp          V->V       Sharpen or blur the input video.
    [173] =>  T.. uspp             V->V       Apply Ultra Simple / Slow Post-processing filter.
    [174] =>  ... vflip            V->V       Flip the input video vertically.
    [175] =>  T.. vignette         V->V       Make or reverse a vignette effect.
    [176] =>  T.. w3fdif           V->V       Apply Martin Weston three field deinterlace.
    [177] =>  .S. xbr              V->V       Scale the input using xBR algorithm.
    [178] =>  TS. yadif            V->V       Deinterlace the input image.
    [179] =>  T.. zoompan          V->V       Apply Zoom & Pan effect.
    [180] =>  ... cellauto         |->V       Create pattern generated by an elementary cellular automaton.
    [181] =>  ..C color            |->V       Provide an uniformly colored input.
    [182] =>  ... haldclutsrc      |->V       Provide an identity Hald CLUT.
    [183] =>  ... life             |->V       Create life.
    [184] =>  ... mandelbrot       |->V       Render a Mandelbrot fractal.
    [185] =>  ... mptestsrc        |->V       Generate various test pattern.
    [186] =>  ... nullsrc          |->V       Null video source, return unprocessed video frames.
    [187] =>  ... rgbtestsrc       |->V       Generate RGB test pattern.
    [188] =>  ... smptebars        |->V       Generate SMPTE color bars.
    [189] =>  ... smptehdbars      |->V       Generate SMPTE HD color bars.
    [190] =>  ... testsrc          |->V       Generate test pattern.
    [191] =>  ... nullsink         V->|       Do absolutely nothing with the input video.
    [192] =>  ... avectorscope     A->V       Convert input audio to vectorscope video output.
    [193] =>  ... concat           N->N       Concatenate audio and video streams.
    [194] =>  ... showcqt          A->V       Convert input audio to a CQT (Constant Q Transform) spectrum video output.
    [195] =>  ... showspectrum     A->V       Convert input audio to a spectrum video output.
    [196] =>  ... showwaves        A->V       Convert input audio to a video output.
    [197] =>  ... amovie           |->N       Read audio from a movie source.
    [198] =>  ... movie            |->N       Read from a movie source.
    [199] =>  ... ffbuffersink     V->|       Buffer video frames, and make them available to the end of the filter graph.
    [200] =>  ... ffabuffersink    A->|       Buffer audio frames, and make them available to the end of the filter graph.
    [201] =>  ... abuffer          |->A       Buffer audio frames, and make them accessible to the filterchain.
    [202] =>  ... buffer           |->V       Buffer video frames, and make them accessible to the filterchain.
    [203] =>  ... abuffersink      A->|       Buffer audio frames, and make them available to the end of the filter graph.
    [204] =>  ... buffersink       V->|       Buffer video frames, and make them available to the end of the filter graph.
    [205] =>  ... afifo            A->A       Buffer input frames and send them when they are requested.
    [206] =>  ... fifo             V->V       Buffer input images and send them when they are requested.
)

... que muestra amix(y con el amergeque también he estado experimentando) pero no complex(¿debería? No lo sé).

Ahora no sé si:

(a) Mi comando es incorrecto

(b) La versión ffmpeg es demasiado antigua para admitir filtros complejos

(c) La configuración del servidor necesita ser cambiada

¡¿Ayuda?!