Codecs

Descriptors

class av.codec.Codec(name, mode='r')

Bases: object

Parameters:

• name (str) – The codec name.

• mode (str) – 'r' for decoding or 'w' for encoding.

This object exposes information about an available codec, and an avenue to create a CodecContext to encode/decode directly.

>>> codec = Codec('mpeg4', 'r')
>>> codec.name
'mpeg4'
>>> codec.type
'video'
>>> codec.is_encoder
False

Codec.create(unicode kind=None)

Create a CodecContext for this codec.

Parameters:

kind (str) – Gives a hint to static type checkers for what exact CodecContext is used.

Codec.is_decoder

Codec.is_encoder

Codec.descriptor

Codec.name

Codec.long_name

Codec.type

The media type of this codec.

E.g: 'audio', 'video', 'subtitle'.

Codec.id

Codec.frame_rates

A list of supported frame rates (fractions.Fraction), or None.

Codec.audio_rates

A list of supported audio sample rates (int), or None.

Codec.video_formats

A list of supported VideoFormat, or None.

Codec.audio_formats

A list of supported AudioFormat, or None.

Flags

Codec.properties

Flag property of Properties

class av.codec.Properties

Bases: EnumFlag

Wraps AVCodecDescriptor.props (AV_CODEC_PROP_*).

Codec Attribute	Properties Name	Flag Value	Meaning in FFmpeg
intra_only	INTRA_ONLY	0x1	Codec uses only intra compression. Video and audio codecs only.
lossy	LOSSY	0x2	Codec supports lossy compression. Audio and video codecs only. Note: A codec may support both lossy and lossless compression modes.
lossless	LOSSLESS	0x4	Codec supports lossless compression. Audio and video codecs only.
reorder	REORDER	0x8	Codec supports frame reordering. That is, the coded order (the order in which the encoded packets are output by the encoders / stored / input to the decoders) may be different from the presentation order of the corresponding frames. For codecs that do not have this property set, PTS and DTS should always be equal.
bitmap_sub	BITMAP_SUB	0x10000	Subtitle codec is bitmap based Decoded AVSubtitle data can be read from the AVSubtitleRect->pict field.
text_sub	TEXT_SUB	0x20000	Subtitle codec is text based. Decoded AVSubtitle data can be read from the AVSubtitleRect->ass field.

Codec.capabilities

Flag property of Capabilities

class av.codec.Capabilities

Bases: EnumFlag

Wraps AVCodec.capabilities (AV_CODEC_CAP_*).

Note that ffmpeg -codecs prefers the properties versions of INTRA_ONLY and LOSSLESS.

Codec Attribute	Capabilities Name	Flag Value	Meaning in FFmpeg
draw_horiz_band	DRAW_HORIZ_BAND	0x1	Decoder can use draw_horiz_band callback.
dr1	DR1	0x2	Codec uses get_buffer() for allocating buffers and supports custom allocators. If not set, it might not use get_buffer() at all or use operations that assume the buffer was allocated by avcodec_default_get_buffer.
hwaccel	HWACCEL	0x10	-
delay	DELAY	0x20	Encoder or decoder requires flushing with NULL input at the end in order to give the complete and correct output. NOTE: If this flag is not set, the codec is guaranteed to never be fed with with NULL data. The user can still send NULL data to the public encode or decode function, but libavcodec will not pass it along to the codec unless this flag is set. Decoders: The decoder has a non-zero delay and needs to be fed with avpkt->data=NULL, avpkt->size=0 at the end to get the delayed data until the decoder no longer returns frames. Encoders: The encoder needs to be fed with NULL data at the end of encoding until the encoder no longer returns data. NOTE: For encoders implementing the AVCodec.encode2() function, setting this flag also means that the encoder must set the pts and duration for each output packet. If this flag is not set, the pts and duration will be determined by libavcodec from the input frame.
small_last_frame	SMALL_LAST_FRAME	0x40	Codec can be fed a final frame with a smaller size. This can be used to prevent truncation of the last audio samples.
hwaccel_vdpau	HWACCEL_VDPAU	0x80	-
subframes	SUBFRAMES	0x100	Codec can output multiple frames per AVPacket Normally demuxers return one frame at a time, demuxers which do not do are connected to a parser to split what they return into proper frames. This flag is reserved to the very rare category of codecs which have a bitstream that cannot be split into frames without timeconsuming operations like full decoding. Demuxers carrying such bitstreams thus may return multiple frames in a packet. This has many disadvantages like prohibiting stream copy in many cases thus it should only be considered as a last resort.
experimental	EXPERIMENTAL	0x200	Codec is experimental and is thus avoided in favor of non experimental encoders
channel_conf	CHANNEL_CONF	0x400	Codec should fill in channel configuration and samplerate instead of container
neg_linesizes	NEG_LINESIZES	0x800	-
frame_threads	FRAME_THREADS	0x1000	Codec supports frame-level multithreading
slice_threads	SLICE_THREADS	0x2000	Codec supports slice-based (or partition-based) multithreading.
param_change	PARAM_CHANGE	0x4000	Codec supports changed parameters at any point.
auto_threads	AUTO_THREADS	0x8000	Codec supports multithreading through a method other than slice- or frame-level multithreading. Typically this marks wrappers around multithreading-capable external libraries.
variable_frame_size	VARIABLE_FRAME_SIZE	0x10000	Audio encoder supports receiving a different number of samples in each call.
avoid_probing	AVOID_PROBING	0x20000	Decoder is not a preferred choice for probing. This indicates that the decoder is not a good choice for probing. It could for example be an expensive to spin up hardware decoder, or it could simply not provide a lot of useful information about the stream. A decoder marked with this flag should only be used as last resort choice for probing.
hardware	HARDWARE	0x40000	Codec is backed by a hardware implementation. Typically used to identify a non-hwaccel hardware decoder. For information about hwaccels, use avcodec_get_hw_config() instead.
hybrid	HYBRID	0x80000	Codec is potentially backed by a hardware implementation, but not necessarily. This is used instead of AV_CODEC_CAP_HARDWARE, if the implementation provides some sort of internal fallback.
encoder_reordered_opaque	ENCODER_REORDERED_OPAQUE	0x100000	This codec takes the reordered_opaque field from input AVFrames and returns it in the corresponding field in AVCodecContext after encoding.
encoder_flush	ENCODER_FLUSH	0x200000	This encoder can be flushed using avcodec_flush_buffers(). If this flag is not set, the encoder must be closed and reopened to ensure that no frames remain pending.

Contexts

class av.codec.context.CodecContext

Bases: object

CodecContext.codec

CodecContext.options

options: dict

static CodecContext.create(codec, mode=None)

CodecContext.open(bool strict=True)

Attributes

CodecContext.is_open

CodecContext.is_encoder

CodecContext.is_decoder

CodecContext.name

CodecContext.type

CodecContext.profile

CodecContext.time_base

CodecContext.bit_rate

CodecContext.bit_rate_tolerance

CodecContext.max_bit_rate

CodecContext.thread_count

How many threads to use; 0 means auto.

Wraps AVCodecContext.thread_count.

CodecContext.thread_type

One of ThreadType.

Wraps AVCodecContext.thread_type.

CodecContext.skip_frame

One of SkipType.

Wraps AVCodecContext.skip_frame.

CodecContext.extradata

CodecContext.extradata_size

Transcoding

CodecContext.parse(raw_input=None)

Split up a byte stream into list of Packet.

This is only effectively splitting up a byte stream, and does no actual interpretation of the data.

It will return all packets that are fully contained within the given input, and will buffer partial packets until they are complete.

Parameters:

raw_input (ByteSource) – A chunk of a byte-stream to process. Anything that can be turned into a ByteSource is fine. None or empty inputs will flush the parser’s buffers.

Returns:

list of Packet newly available.

CodecContext.encode(Frame frame=None)

Encode a list of Packet from the given Frame.

CodecContext.decode(Packet packet=None)

Decode a list of Frame from the given Packet.

If the packet is None, the buffers will be flushed. This is useful if you do not want the library to automatically re-order frames for you (if they are encoded with a codec that has B-frames).

CodecContext.flush_buffers()

Reset the internal codec state and discard all internal buffers.

Should be called before you start decoding from a new position e.g. when seeking or when switching to a different stream.

Flags

CodecContext.flags

Flag property of Flags.

class av.codec.context.Flags

Bases: EnumFlag

CodecContext Attribute	Flags Name	Flag Value	Meaning in FFmpeg
unaligned	UNALIGNED	0x1	Allow decoders to produce frames with data planes that are not aligned to CPU requirements (e.g. due to cropping).
qscale	QSCALE	0x2	Use fixed qscale.
four_mv	4MV	0x4	4 MV per MB allowed / advanced prediction for H.263.
output_corrupt	OUTPUT_CORRUPT	0x8	Output even those frames that might be corrupted.
qpel	QPEL	0x10	Use qpel MC.
drop_changed	DROPCHANGED	0x20	Don’t output frames whose parameters differ from first decoded frame in stream.
recon_frame	RECON_FRAME	0x40	Request the encoder to output reconstructed frames, i.e. frames that would be produced by decoding the encoded bistream.
copy_opaque	COPY_OPAQUE	0x80	Request the decoder to propagate each packet’s AVPacket.opaque and AVPacket.opaque_ref to its corresponding output AVFrame. Request the encoder to propagate each frame’s AVFrame.opaque and AVFrame.opaque_ref values to its corresponding output AVPacket.
frame_duration	FRAME_DURATION	0x100	Signal to the encoder that the values of AVFrame.duration are valid and should be used (typically for transferring them to output packets).
pass1	PASS1	0x200	Use internal 2pass ratecontrol in first pass mode.
pass2	PASS2	0x400	Use internal 2pass ratecontrol in second pass mode.
loop_filter	LOOP_FILTER	0x800	loop filter.
gray	GRAY	0x2000	Only decode/encode grayscale.
psnr	PSNR	0x8000	error[?] variables will be set during encoding.
interlaced_dct	INTERLACED_DCT	0x40000	Use interlaced DCT.
low_delay	LOW_DELAY	0x80000	Force low delay.
global_header	GLOBAL_HEADER	0x400000	Place global headers in extradata instead of every keyframe.
bitexact	BITEXACT	0x800000	Use only bitexact stuff (except (I)DCT).
ac_pred	AC_PRED	0x1000000	H.263 advanced intra coding / MPEG-4 AC prediction
interlaced_me	INTERLACED_ME	0x20000000	Interlaced motion estimation
closed_gop	CLOSED_GOP	0x-80000000	-

CodecContext.flags2

Flag property of Flags2.

class av.codec.context.Flags2

Bases: EnumFlag

CodecContext Attribute	Flags2 Name	Flag Value	Meaning in FFmpeg
fast	FAST	0x1	Allow non spec compliant speedup tricks.
no_output	NO_OUTPUT	0x4	Skip bitstream encoding.
local_header	LOCAL_HEADER	0x8	Place global headers at every keyframe instead of in extradata.
chunks	CHUNKS	0x8000	Input bitstream might be truncated at a packet boundaries instead of only at frame boundaries.
ignore_crop	IGNORE_CROP	0x10000	Discard cropping information from SPS.
show_all	SHOW_ALL	0x400000	Show all frames before the first keyframe
export_mvs	EXPORT_MVS	0x10000000	Export motion vectors through frame side data
skip_manual	SKIP_MANUAL	0x20000000	Do not skip samples and export skip information as frame side data
ro_flush_noop	RO_FLUSH_NOOP	0x40000000	Do not reset ASS ReadOrder field on flush (subtitles decoding)

Enums

class av.codec.context.ThreadType

Bases: EnumFlag

Which multithreading methods to use. Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread, so clients which cannot provide future frames should not use it.

ThreadType Name	Flag Value	Meaning in FFmpeg
NONE	0x0	-
FRAME	0x1	Decode more than one frame at once
SLICE	0x2	Decode more than one part of a single frame at once
AUTO	0x3	Decode using both FRAME and SLICE methods.

class av.codec.context.SkipType

Bases: EnumItem

SkipType Name	Flag Value	Meaning in FFmpeg
NONE	0x-10	Discard nothing
DEFAULT	0x0	Discard useless packets like 0 size packets in AVI
NONREF	0x8	Discard all non reference
BIDIR	0x10	Discard all bidirectional frames
NONINTRA	0x18	Discard all non intra frames
NONKEY	0x20	Discard all frames except keyframes
ALL	0x30	Discard all