1. Synopsis

The generic syntax is:

ffprobe [options] [‘input_file’]

2. Description

FFprobe gathers information from multimedia streams and prints it in human- and machine-readable fashion.

For example it can be used to check the format of the container used by a multimedia stream and the format and type of each media stream contained in it.

If a filename is specified in input, ffprobe will try to open and probe the file content. If the file cannot be opened or recognized as a multimedia file, a positive exit code is returned.

FFprobe may be employed both as a standalone application or in combination with a textual filter, which may perform more sophisticated processing, e.g. statistical processing or plotting.

Options are used to list some of the formats supported by ffprobe or for specifying which information to display, and for setting how ffprobe will show it.

FFprobe output is designed to be easily parsable by a textual filter, and consists of one or more sections of the form:

[SECTION]
key1=val1
...
keyN=valN
[/SECTION]

Metadata tags stored in the container or in the streams are recognized and printed in the corresponding "FORMAT" or "STREAM" section, and are prefixed by the string "TAG:".

3. Options

All the numerical options, if not specified otherwise, accept in input a string representing a number, which may contain one of the International System number postfixes, for example 'K', 'M', 'G'. If 'i' is appended after the postfix, powers of 2 are used instead of powers of 10. The 'B' postfix multiplies the value for 8, and can be appended after another postfix or used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as postfix.

Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing with "no" the option name, for example using "-nofoo" in the commandline will set to false the boolean option with name "foo".

3.1 Generic options

These options are shared amongst the ff* tools.

‘-L’

Show license.

‘-h, -?, -help, --help’

Show help.

‘-version’

Show version.

‘-formats’

Show available formats.

The fields preceding the format names have the following meanings:

‘D’

Decoding available

‘E’

Encoding available

‘-codecs’

Show available codecs.

The fields preceding the codec names have the following meanings:

‘D’

Decoding available

‘E’

Encoding available

‘V/A/S’

Video/audio/subtitle codec

‘S’

Codec supports slices

‘D’

Codec supports direct rendering

‘T’

Codec can handle input truncated at random locations instead of only at frame boundaries

‘-bsfs’

Show available bitstream filters.

‘-protocols’

Show available protocols.

‘-filters’

Show available libavfilter filters.

‘-pix_fmts’

Show available pixel formats.

‘-loglevel loglevel’

Set the logging level used by the library. loglevel is a number or a string containing one of the following values:

‘quiet’

‘panic’

‘fatal’

‘error’

‘warning’

‘info’

‘verbose’

‘debug’

By default the program logs to stderr, if coloring is supported by the terminal, colors are used to mark errors and warnings. Log coloring can be disabled setting the environment variable NO_COLOR.

3.2 Main options

‘-f format’

Force format to use.

‘-unit’

Show the unit of the displayed values.

‘-prefix’

Use SI prefixes for the displayed values. Unless the "-byte_binary_prefix" option is used all the prefixes are decimal.

‘-byte_binary_prefix’

Force the use of binary prefixes for byte values.

‘-sexagesimal’

Use sexagesimal format HH:MM:SS.MICROSECONDS for time values.

‘-pretty’

Prettify the format of the displayed values, it corresponds to the options "-unit -prefix -byte_binary_prefix -sexagesimal".

‘-show_format’

Show information about the container format of the input multimedia stream.

All the container format information is printed within a section with name "FORMAT".

‘-show_packets’

Show information about each packet contained in the input multimedia stream.

The information for each single packet is printed within a dedicated section with name "PACKET".

‘-show_streams’

Show information about each media stream contained in the input multimedia stream.

Each media stream information is printed within a dedicated section with name "STREAM".

4. Protocols

Protocols are configured elements in FFmpeg which allow to access resources which require the use of a particular protocol.

When you configure your FFmpeg build, all the supported protocols are enabled by default. You can list all available ones using the configure option "–list-protocols".

You can disable all the protocols using the configure option "–disable-protocols", and selectively enable a protocol using the option "–enable-protocol=PROTOCOL", or you can disable a particular protocol using the option "–disable-protocol=PROTOCOL".

The option "-protocols" of the ff* tools will display the list of supported protocols.

A description of the currently available protocols follows.

4.1 concat

Physical concatenation protocol.

Allow to read and seek from many resource in sequence as if they were a unique resource.

A URL accepted by this protocol has the syntax:

concat:URL1|URL2|...|URLN

where URL1, URL2, ..., URLN are the urls of the resource to be concatenated, each one possibly specifying a distinct protocol.

For example to read a sequence of files ‘split1.mpeg’, ‘split2.mpeg’, ‘split3.mpeg’ with ‘ffplay’ use the command:

ffplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg

Note that you may need to escape the character "|" which is special for many shells.

4.2 file

File access protocol.

Allow to read from or read to a file.

For example to read from a file ‘input.mpeg’ with ‘ffmpeg’ use the command:

ffmpeg -i file:input.mpeg output.mpeg

The ff* tools default to the file protocol, that is a resource specified with the name "FILE.mpeg" is interpreted as the URL "file:FILE.mpeg".

4.3 gopher

Gopher protocol.

4.4 http

HTTP (Hyper Text Transfer Protocol).

4.5 mmst

MMS (Microsoft Media Server) protocol over TCP.

4.6 mmsh

MMS (Microsoft Media Server) protocol over HTTP.

The required syntax is:

mmsh://server[:port][/app][/playpath]

4.7 md5

MD5 output protocol.

Computes the MD5 hash of the data to be written, and on close writes this to the designated output or stdout if none is specified. It can be used to test muxers without writing an actual file.

Some examples follow.

# Write the MD5 hash of the encoded AVI file to the file output.avi.md5.
ffmpeg -i input.flv -f avi -y md5:output.avi.md5

# Write the MD5 hash of the encoded AVI file to stdout.
ffmpeg -i input.flv -f avi -y md5:

Note that some formats (typically MOV) require the output protocol to be seekable, so they will fail with the MD5 output protocol.

4.8 pipe

UNIX pipe access protocol.

Allow to read and write from UNIX pipes.

The accepted syntax is:

pipe:[number]

number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.

For example to read from stdin with ‘ffmpeg’:

cat test.wav | ffmpeg -i pipe:0
# ...this is the same as...
cat test.wav | ffmpeg -i pipe:

For writing to stdout with ‘ffmpeg’:

ffmpeg -i test.wav -f avi pipe:1 | cat > test.avi
# ...this is the same as...
ffmpeg -i test.wav -f avi pipe: | cat > test.avi

Note that some formats (typically MOV), require the output protocol to be seekable, so they will fail with the pipe output protocol.

4.9 rtmp

Real-Time Messaging Protocol.

The Real-Time Messaging Protocol (RTMP) is used for streaming multime‐ dia content across a TCP/IP network.

The required syntax is:

rtmp://server[:port][/app][/playpath]

The accepted parameters are:

‘server’

The address of the RTMP server.

‘port’

The number of the TCP port to use (by default is 1935).

‘app’

It is the name of the application to access. It usually corresponds to the path where the application is installed on the RTMP server (e.g. ‘/ondemand/’, ‘/flash/live/’, etc.).

‘playpath’

It is the path or name of the resource to play with reference to the application specified in app, may be prefixed by "mp4:".

For example to read with ‘ffplay’ a multimedia resource named "sample" from the application "vod" from an RTMP server "myserver":

ffplay rtmp://myserver/vod/sample

4.10 rtmp, rtmpe, rtmps, rtmpt, rtmpte

Real-Time Messaging Protocol and its variants supported through librtmp.

Requires the presence of the librtmp headers and library during configuration. You need to explicitely configure the build with "–enable-librtmp". If enabled this will replace the native RTMP protocol.

This protocol provides most client functions and a few server functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT), encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled variants of these encrypted types (RTMPTE, RTMPTS).

The required syntax is:

rtmp_proto://server[:port][/app][/playpath] options

where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe", "rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and server, port, app and playpath have the same meaning as specified for the RTMP native protocol. options contains a list of space-separated options of the form key=val.

See the librtmp manual page (man 3 librtmp) for more information.

For example, to stream a file in real-time to an RTMP server using ‘ffmpeg’:

ffmpeg -re -i myfile -f flv rtmp://myserver/live/mystream

To play the same stream using ‘ffplay’:

ffplay "rtmp://myserver/live/mystream live=1"

4.11 rtp

Real-Time Protocol.

4.12 rtsp

RTSP is not technically a protocol handler in libavformat, it is a demuxer and muxer. The demuxer supports both normal RTSP (with data transferred over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with data transferred over RDT).

The muxer can be used to send a stream using RTSP ANNOUNCE to a server supporting it (currently Darwin Streaming Server and Mischa Spiegelmock's RTSP server, http://github.com/revmischa/rtsp-server).

The required syntax for a RTSP url is:

rtsp://hostname[:port]/path[?options]

options is a &-separated list. The following options are supported:

‘udp’

Use UDP as lower transport protocol.

‘tcp’

Use TCP (interleaving within the RTSP control channel) as lower transport protocol.

‘multicast’

Use UDP multicast as lower transport protocol.

‘http’

Use HTTP tunneling as lower transport protocol, which is useful for passing proxies.

Multiple lower transport protocols may be specified, in that case they are tried one at a time (if the setup of one fails, the next one is tried). For the muxer, only the tcp and udp options are supported.

When receiving data over UDP, the demuxer tries to reorder received packets (since they may arrive out of order, or packets may get lost totally). In order for this to be enabled, a maximum delay must be specified in the max_delay field of AVFormatContext.

When watching multi-bitrate Real-RTSP streams with ‘ffplay’, the streams to display can be chosen with -vst n and -ast n for video and audio respectively, and can be switched on the fly by pressing v and a.

Example command lines:

To watch a stream over UDP, with a max reordering delay of 0.5 seconds:

ffplay -max_delay 500000 rtsp://server/video.mp4?udp

To watch a stream tunneled over HTTP:

ffplay rtsp://server/video.mp4?http

To send a stream in realtime to a RTSP server, for others to watch:

ffmpeg -re -i input -f rtsp -muxdelay 0.1 rtsp://server/live.sdp

4.13 sap

Session Announcement Protocol (RFC 2974). This is not technically a protocol handler in libavformat, it is a muxer and demuxer. It is used for signalling of RTP streams, by announcing the SDP for the streams regularly on a separate port.

4.13.1 Muxer

The syntax for a SAP url given to the muxer is:

sap://destination[:port][?options]

The RTP packets are sent to destination on port port, or to port 5004 if no port is specified. options is a &-separated list. The following options are supported:

‘announce_addr=address’

Specify the destination IP address for sending the announcements to. If omitted, the announcements are sent to the commonly used SAP announcement multicast address 224.2.127.254 (sap.mcast.net), or ff0e::2:7ffe if destination is an IPv6 address.

‘announce_port=port’

Specify the port to send the announcements on, defaults to 9875 if not specified.

‘ttl=ttl’

Specify the time to live value for the announcements and RTP packets, defaults to 255.

‘same_port=0|1’

If set to 1, send all RTP streams on the same port pair. If zero (the default), all streams are sent on unique ports, with each stream on a port 2 numbers higher than the previous. VLC/Live555 requires this to be set to 1, to be able to receive the stream. The RTP stack in libavformat for receiving requires all streams to be sent on unique ports.

Example command lines follow.

To broadcast a stream on the local subnet, for watching in VLC:

ffmpeg -re -i input -f sap sap://224.0.0.255?same_port=1

Similarly, for watching in ffplay:

ffmpeg -re -i input -f sap sap://224.0.0.255

And for watching in ffplay, over IPv6:

ffmpeg -re -i input -f sap sap://[ff0e::1:2:3:4]

4.13.2 Demuxer

The syntax for a SAP url given to the demuxer is:

sap://[address][:port]

address is the multicast address to listen for announcements on, if omitted, the default 224.2.127.254 (sap.mcast.net) is used. port is the port that is listened on, 9875 if omitted.

The demuxers listens for announcements on the given address and port. Once an announcement is received, it tries to receive that particular stream.

Example command lines follow.

To play back the first stream announced on the normal SAP multicast address:

ffplay sap://

To play back the first stream announced on one the default IPv6 SAP multicast address:

ffplay sap://[ff0e::2:7ffe]

4.14 tcp

Trasmission Control Protocol.

4.15 udp

User Datagram Protocol.

The required syntax for a UDP url is:

udp://hostname:port[?options]

options contains a list of &-seperated options of the form key=val. Follow the list of supported options.

‘buffer_size=size’

set the UDP buffer size in bytes

‘localport=port’

override the local UDP port to bind with

‘pkt_size=size’

set the size in bytes of UDP packets

‘reuse=1|0’

explicitly allow or disallow reusing UDP sockets

‘ttl=ttl’

set the time to live value (for multicast only)

‘connect=1|0’

Initialize the UDP socket with connect(). In this case, the destination address can't be changed with udp_set_remote_url later. This allows finding out the source address for the packets with getsockname, and makes writes return with AVERROR(ECONNREFUSED) if "destination unreachable" is received.

Some usage examples of the udp protocol with ‘ffmpeg’ follow.

To stream over UDP to a remote endpoint:

ffmpeg -i input -f format udp://hostname:port

To stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:

ffmpeg -i input -f mpegts udp://hostname:port?pkt_size=188&buffer_size=65535

To receive over UDP from a remote endpoint:

ffmpeg -i udp://[multicast-address]:port

5. Input Devices

Input devices are configured elements in FFmpeg which allow to access the data coming from a multimedia device attached to your system.

When you configure your FFmpeg build, all the supported input devices are enabled by default. You can list all available ones using the configure option "–list-indevs".

You can disable all the input devices using the configure option "–disable-indevs", and selectively enable an input device using the option "–enable-indev=INDEV", or you can disable a particular input device using the option "–disable-indev=INDEV".

The option "-formats" of the ff* tools will display the list of supported input devices (amongst the demuxers).

A description of the currently available input devices follows.

5.1 alsa

ALSA (Advanced Linux Sound Architecture) input device.

To enable this input device during configuration you need libasound installed on your system.

This device allows capturing from an ALSA device. The name of the device to capture has to be an ALSA card identifier.

An ALSA identifier has the syntax:

hw:CARD[,DEV[,SUBDEV]]

where the DEV and SUBDEV components are optional.

The three arguments (in order: CARD,DEV,SUBDEV) specify card number or identifier, device number and subdevice number (-1 means any).

To see the list of cards currently recognized by your system check the files ‘/proc/asound/cards’ and ‘/proc/asound/devices’.

For example to capture with ‘ffmpeg’ from an ALSA device with card id 0, you may run the command:

ffmpeg -f alsa -i hw:0 alsaout.wav

For more information see: http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html

5.2 bktr

BSD video input device.

5.3 dv1394

Linux DV 1394 input device.

5.4 jack

JACK input device.

To enable this input device during configuration you need libjack installed on your system.

A JACK input device creates one or more JACK writable clients, one for each audio channel, with name client_name:input_N, where client_name is the name provided by the application, and N is a number which identifies the channel. Each writable client will send the acquired data to the FFmpeg input device.

Once you have created one or more JACK readable clients, you need to connect them to one or more JACK writable clients.

To connect or disconnect JACK clients you can use the ‘jack_connect’ and ‘jack_disconnect’ programs, or do it through a graphical interface, for example with ‘qjackctl’.

To list the JACK clients and their properties you can invoke the command ‘jack_lsp’.

Follows an example which shows how to capture a JACK readable client with ‘ffmpeg’.

# Create a JACK writable client with name "ffmpeg".
$ ffmpeg -f jack -i ffmpeg -y out.wav

# Start the sample jack_metro readable client.
$ jack_metro -b 120 -d 0.2 -f 4000

# List the current JACK clients.
$ jack_lsp -c
system:capture_1
system:capture_2
system:playback_1
system:playback_2
ffmpeg:input_1
metro:120_bpm

# Connect metro to the ffmpeg writable client.
$ jack_connect metro:120_bpm ffmpeg:input_1

For more information read: http://jackaudio.org/

5.5 libdc1394

IIDC1394 input device, based on libdc1394 and libraw1394.

5.6 oss

Open Sound System input device.

The filename to provide to the input device is the device node representing the OSS input device, and is usually set to ‘/dev/dsp’.

For example to grab from ‘/dev/dsp’ using ‘ffmpeg’ use the command:

ffmpeg -f oss -i /dev/dsp /tmp/oss.wav

For more information about OSS see: http://manuals.opensound.com/usersguide/dsp.html

5.7 video4linux and video4linux2

Video4Linux and Video4Linux2 input video devices.

The name of the device to grab is a file device node, usually Linux systems tend to automatically create such nodes when the device (e.g. an USB webcam) is plugged into the system, and has a name of the kind ‘/dev/videoN’, where N is a number associated to the device.

Video4Linux and Video4Linux2 devices only support a limited set of widthxheight sizes and framerates. You can check which are supported for example with the command ‘dov4l’ for Video4Linux devices and the command ‘v4l-info’ for Video4Linux2 devices.

If the size for the device is set to 0x0, the input device will try to autodetect the size to use.

Video4Linux support is deprecated since Linux 2.6.30, and will be dropped in later versions.

Follow some usage examples of the video4linux devices with the ff* tools.

# Grab and show the input of a video4linux device.
ffplay -s 320x240 -f video4linux /dev/video0

# Grab and show the input of a video4linux2 device, autoadjust size.
ffplay -f video4linux2 /dev/video0

# Grab and record the input of a video4linux2 device, autoadjust size.
ffmpeg -f video4linux2 -i /dev/video0 out.mpeg

5.8 vfwcap

VfW (Video for Windows) capture input device.

5.9 x11grab

X11 video input device.

This device allows to capture a region of an X11 display.

The filename passed as input has the syntax:

[hostname]:display_number.screen_number[+x_offset,y_offset]

hostname:display_number.screen_number specifies the X11 display name of the screen to grab from. hostname can be ommitted, and defaults to "localhost". The environment variable DISPLAY contains the default display name.

x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the X11 screen. They default to 0.

Check the X11 documentation (e.g. man X) for more detailed information.

Use the ‘dpyinfo’ program for getting basic information about the properties of your X11 display (e.g. grep for "name" or "dimensions").

For example to grab from ‘:0.0’ using ‘ffmpeg’:

ffmpeg -f x11grab -r 25 -s cif -i :0.0 out.mpg

# Grab at position 10,20.
ffmpeg -f x11grab -25 -s cif -i :0.0+10,20 out.mpg

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