ffmpeg-utils - FFmpeg utilities This document describes some generic features and utilities provided by the libavutil library. This section documents the syntax and formats employed by the FFmpeg libraries and tools.

Quoting and escaping
FFmpeg adopts the following quoting and escaping mechanism, unless explicitly specified. The following rules are applied: ' and \ are special characters (respectively used for quoting and escaping). In addition to them, there might be other special characters depending on the specific syntax where the escaping and quoting are employed. A special character is escaped by prefixing it with a \. All characters enclosed between '' are included literally in the parsed string. The quote character ' itself cannot be quoted, so you may need to close the quote and escape it. Leading and trailing whitespaces, unless escaped or quoted, are removed from the parsed string. Note that you may need to add a second level of escaping when using the command line or a script, which depends on the syntax of the adopted shell language. The function "av_get_token" defined in libavutil/avstring.h can be used to parse a token quoted or escaped according to the rules defined above. The tool tools/ffescape in the FFmpeg source tree can be used to automatically quote or escape a string in a script. Examples Escape the string "Crime d'Amour" containing the "'" special character: Crime d\'Amour The string above contains a quote, so the "'" needs to be escaped when quoting it: 'Crime d'\''Amour' Include leading or trailing whitespaces using quoting: ' this string starts and ends with whitespaces ' Escaping and quoting can be mixed together: ' The string '\'string\'' is a string ' To include a literal \ you can use either escaping or quoting: 'c:\foo' can be written as c:\\foo

Date
The accepted syntax is: [(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z] now If the value is "now" it takes the current time. Time is local time unless Z is appended, in which case it is interpreted as UTC. If the year-month-day part is not specified it takes the current year-month-day.

Time duration
There are two accepted syntaxes for expressing time duration. [-][<HH>:]<MM>:<SS>[.<m>...] HH expresses the number of hours, MM the number of minutes for a maximum of 2 digits, and SS the number of seconds for a maximum of 2 digits. The m at the end expresses decimal value for SS. or [-]<S>+[.<m>...][s|ms|us] S expresses the number of seconds, with the optional decimal part m. The optional literal suffixes s, ms or us indicate to interpret the value as seconds, milliseconds or microseconds, respectively. In both expressions, the optional - indicates negative duration. Examples The following examples are all valid time duration: 55 seconds 0.2 seconds 200 milliseconds, that's 0.2s 200000 microseconds, that's 0.2s 12 hours, 03 minutes and 45 seconds 23.189 seconds

Video size
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation. The following abbreviations are recognized: 720x480 720x576 352x240 352x288 640x480 768x576 352x240 352x240 128x96 176x144 352x288 704x576 1408x1152 160x120 320x240 640x480 800x600 1024x768 1600x1200 2048x1536 1280x1024 2560x2048 5120x4096 852x480 1366x768 1600x1024 1920x1200 2560x1600 3200x2048 3840x2400 6400x4096 7680x4800 320x200 640x350 852x480 1280x720 1920x1080 2048x1080 1998x1080 2048x858 4096x2160 3996x2160 4096x1716 640x360 240x160 400x240 432x240 480x320 960x540 2048x1080 4096x2160 3840x2160 7680x4320

Video rate
Specify the frame rate of a video, expressed as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation. The following abbreviations are recognized: 30000/1001 25/1 30000/1001 25/1 30000/1001 25/1 24/1 24000/1001

Ratio
A ratio can be expressed as an expression, or in the form numerator:denominator. Note that a ratio with infinite (1/0) or negative value is considered valid, so you should check on the returned value if you want to exclude those values. The undefined value can be expressed using the "0:0" string.

Color
It can be the name of a color as defined below (case insensitive match) or a "[0x|#]RRGGBB[AA]" sequence, possibly followed by @ and a string representing the alpha component. The alpha component may be a string composed by "0x" followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (0x00 or 0.0 means completely transparent, 0xff or 1.0 completely opaque). If the alpha component is not specified then 0xff is assumed. The string random will result in a random color. The following names of colors are recognized: 0xF0F8FF 0xFAEBD7 0x00FFFF 0x7FFFD4 0xF0FFFF 0xF5F5DC 0xFFE4C4 0x000000 0xFFEBCD 0x0000FF 0x8A2BE2 0xA52A2A 0xDEB887 0x5F9EA0 0x7FFF00 0xD2691E 0xFF7F50 0x6495ED 0xFFF8DC 0xDC143C 0x00FFFF 0x00008B 0x008B8B 0xB8860B 0xA9A9A9 0x006400 0xBDB76B 0x8B008B 0x556B2F 0xFF8C00 0x9932CC 0x8B0000 0xE9967A 0x8FBC8F 0x483D8B 0x2F4F4F 0x00CED1 0x9400D3 0xFF1493 0x00BFFF 0x696969 0x1E90FF 0xB22222 0xFFFAF0 0x228B22 0xFF00FF 0xDCDCDC 0xF8F8FF 0xFFD700 0xDAA520 0x808080 0x008000 0xADFF2F 0xF0FFF0 0xFF69B4 0xCD5C5C 0x4B0082 0xFFFFF0 0xF0E68C 0xE6E6FA 0xFFF0F5 0x7CFC00 0xFFFACD 0xADD8E6 0xF08080 0xE0FFFF 0xFAFAD2 0x90EE90 0xD3D3D3 0xFFB6C1 0xFFA07A 0x20B2AA 0x87CEFA 0x778899 0xB0C4DE 0xFFFFE0 0x00FF00 0x32CD32 0xFAF0E6 0xFF00FF 0x800000 0x66CDAA 0x0000CD 0xBA55D3 0x9370D8 0x3CB371 0x7B68EE 0x00FA9A 0x48D1CC 0xC71585 0x191970 0xF5FFFA 0xFFE4E1 0xFFE4B5 0xFFDEAD 0x000080 0xFDF5E6 0x808000 0x6B8E23 0xFFA500 0xFF4500 0xDA70D6 0xEEE8AA 0x98FB98 0xAFEEEE 0xD87093 0xFFEFD5 0xFFDAB9 0xCD853F 0xFFC0CB 0xDDA0DD 0xB0E0E6 0x800080 0xFF0000 0xBC8F8F 0x4169E1 0x8B4513 0xFA8072 0xF4A460 0x2E8B57 0xFFF5EE 0xA0522D 0xC0C0C0 0x87CEEB 0x6A5ACD 0x708090 0xFFFAFA 0x00FF7F 0x4682B4 0xD2B48C 0x008080 0xD8BFD8 0xFF6347 0x40E0D0 0xEE82EE 0xF5DEB3 0xFFFFFF 0xF5F5F5 0xFFFF00 0x9ACD32

Channel Layout
A channel layout specifies the spatial disposition of the channels in a multi-channel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax. Individual channels are identified by an id, as given by the table below: front left front right front center low frequency back left back right front left-of-center front right-of-center back center side left side right top center top front left top front center top front right top back left top back center top back right downmix left downmix right wide left wide right surround direct left surround direct right low frequency 2 Standard channel layout compositions can be specified by using the following identifiers: FC FL+FR FL+FR+LFE FL+FR+FC FL+FR+BC FL+FR+FC+BC FL+FR+BL+BR FL+FR+SL+SR FL+FR+FC+LFE FL+FR+FC+BL+BR FL+FR+FC+SL+SR FL+FR+FC+LFE+BC FL+FR+FC+LFE+BL+BR FL+FR+FC+LFE+SL+SR FL+FR+FC+BC+SL+SR FL+FR+FLC+FRC+SL+SR FL+FR+FC+LFE+TFL+TFR FL+FR+FC+BL+BR+BC FL+FR+FC+LFE+BC+SL+SR FL+FR+FC+LFE+BL+BR+BC FL+FR+LFE+FLC+FRC+SL+SR FL+FR+FC+BL+BR+SL+SR FL+FR+FC+FLC+FRC+SL+SR FL+FR+FC+LFE+BL+BR+SL+SR FL+FR+FC+LFE+BL+BR+FLC+FRC FL+FR+FC+LFE+FLC+FRC+SL+SR FL+FR+FC+LFE+BL+BR+TFL+TFR FL+FR+FC+BL+BR+BC+SL+SR FL+FR+BL+BR+TFL+TFR+TBL+TBR FL+FR+FC+LFE+BL+BR+TFL+TFR+TBL+TBR FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBL+TBR FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBC+LFE2 FL+FR+FC+LFE+BL+BR+FLC+FRC+SL+SR+TFL+TFR+TBL+TBR FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR DL+DR FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR A custom channel layout can be specified as a sequence of terms, separated by '+'. Each term can be: the name of a single channel (e.g. FL, FR, FC, LFE, etc.), each optionally containing a custom name after a '@', (e.g. FL@Left, FR@Right, FC@Center, LFE@Low_Frequency, etc.) A standard channel layout can be specified by the following: the name of a single channel (e.g. FL, FR, FC, LFE, etc.) the name of a standard channel layout (e.g. mono, stereo, 4.0, quad, 5.0, etc.) a number of channels, in decimal, followed by 'c', yielding the default channel layout for that number of channels (see the function "av_channel_layout_default"). Note that not all channel counts have a default layout. a number of channels, in decimal, followed by 'C', yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts. a channel layout mask, in hexadecimal starting with "0x" (see the "AV_CH_*" macros in libavutil/channel_layout.h. Before libavutil version 53 the trailing character "c" to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by "c" or "C"). See also the function "av_channel_layout_from_string" defined in libavutil/channel_layout.h. When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the libavutil/eval.h interface. An expression may contain unary, binary operators, constants, and functions. Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2. The following binary operators are available: "+", "-", "*", "/", "^". The following unary operators are available: "+", "-". Some internal variables can be used to store and load intermediary results. They can be accessed using the "ld" and "st" functions with an index argument varying from 0 to 9 to specify which internal variable to access. The following functions are available: Compute absolute value of x. Compute arccosine of x. Compute arcsine of x. Compute arctangent of x. Compute principal value of the arc tangent of y/x. Return 1 if x is greater than or equal to min and lesser than or equal to max, 0 otherwise. Compute bitwise and/or operation on x and y. The results of the evaluation of x and y are converted to integers before executing the bitwise operation. Note that both the conversion to integer and the conversion back to floating point can lose precision. Beware of unexpected results for large numbers (usually 2^53 and larger). Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0". Return the value of x clipped between min and max. Compute cosine of x. Compute hyperbolic cosine of x. Return 1 if x and y are equivalent, 0 otherwise. Compute exponential of x (with base "e", the Euler's number). Round the value of expression expr downwards to the nearest integer. For example, "floor(-1.5)" is "-2.0". Compute Gauss function of x, corresponding to "exp(-x*x/2) / sqrt(2*PI)". Return the greatest common divisor of x and y. If both x and y are 0 or either or both are less than zero then behavior is undefined. Return 1 if x is greater than y, 0 otherwise. Return 1 if x is greater than or equal to y, 0 otherwise. This function is similar to the C function with the same name; it returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin. Evaluate x, and if the result is non-zero return the result of the evaluation of y, return 0 otherwise. Evaluate x, and if the result is non-zero return the evaluation result of y, otherwise the evaluation result of z. Evaluate x, and if the result is zero return the result of the evaluation of y, return 0 otherwise. Evaluate x, and if the result is zero return the evaluation result of y, otherwise the evaluation result of z. Return 1.0 if x is +/-INFINITY, 0.0 otherwise. Return 1.0 if x is NAN, 0.0 otherwise. Load the value of the internal variable with index idx, which was previously stored with st(idx, expr). The function returns the loaded value. Return linear interpolation between x and y by amount of z. Compute natural logarithm of x. Return 1 if x is lesser than y, 0 otherwise. Return 1 if x is lesser than or equal to y, 0 otherwise. Return the maximum between x and y. Return the minimum between x and y. Compute the remainder of division of x by y. Return 1.0 if expr is zero, 0.0 otherwise. Compute the power of x elevated y, it is equivalent to "(x)^(y)". Print the value of expression t with loglevel l. If l is not specified then a default log level is used. Return the value of the expression printed. Return a pseudo random value between 0.0 and 1.0. idx is the index of the internal variable used to save the seed/state, which can be previously stored with "st(idx)". To initialize the seed, you need to store the seed value as a 64-bit unsigned integer in the internal variable with index idx. For example, to store the seed with value 42 in the internal variable with index 0 and print a few random values: st(0,42); print(random(0)); print(random(0)); print(random(0)) Return a pseudo random value in the interval between min and max. idx is the index of the internal variable which will be used to save the seed/state, which can be previously stored with "st(idx)". To initialize the seed, you need to store the seed value as a 64-bit unsigned integer in the internal variable with index idx. Find an input value for which the function represented by expr with argument ld(0) is 0 in the interval 0..max. The expression in expr must denote a continuous function or the result is undefined. ld(0) is used to represent the function input value, which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(0). When the expression evaluates to 0 then the corresponding input value will be returned. Round the value of expression expr to the nearest integer. For example, "round(1.5)" is "2.0". Compute sign of x. Compute sine of x. Compute hyperbolic sine of x. Compute the square root of expr. This is equivalent to "(expr)^.5". Compute expression "1/(1 + exp(4*x))". Store the value of the expression expr in an internal variable. idx specifies the index of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable. The stored value can be retrieved with "ld(var)". Note: variables are currently not shared between expressions. Compute tangent of x. Compute hyperbolic tangent of x. Evaluate a Taylor series at x, given an expression representing the "ld(idx)"-th derivative of a function at 0. When the series does not converge the result is undefined. ld(idx) is used to represent the derivative order in expr, which means that the given expression will be evaluated multiple times with various input values that the expression can access through "ld(idx)". If idx is not specified then 0 is assumed. Note, when you have the derivatives at y instead of 0, "taylor(expr, x-y)" can be used. Return the current (wallclock) time in seconds. Round the value of expression expr towards zero to the nearest integer. For example, "trunc(-1.5)" is "-1.0". Evaluate expression expr while the expression cond is non-zero, and returns the value of the last expr evaluation, or NAN if cond was always false. The following constants are available: area of the unit disc, approximately 3.14 exp(1) (Euler's number), approximately 2.718 golden ratio (1+sqrt(5))/2, approximately 1.618 Assuming that an expression is considered "true" if it has a non-zero value, note that: "*" works like AND "+" works like OR For example the construct: if (A AND B) then C is equivalent to: if(A*B, C) In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions. The evaluator also recognizes the International System unit prefixes. If 'i' is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The 'B' postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as number postfix. The list of available International System prefixes follows, with indication of the corresponding powers of 10 and of 2. 10^-24 / 2^-80 10^-21 / 2^-70 10^-18 / 2^-60 10^-15 / 2^-50 10^-12 / 2^-40 10^-9 / 2^-30 10^-6 / 2^-20 10^-3 / 2^-10 10^-2 10^-1 10^2 10^3 / 2^10 10^3 / 2^10 10^6 / 2^20 10^9 / 2^30 10^12 / 2^40 10^15 / 2^50 10^18 / 2^60 10^21 / 2^70 10^24 / 2^80 ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3) The FFmpeg developers. For details about the authorship, see the Git history of the project (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at <https://git.ffmpeg.org/ffmpeg>. Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.