AVInputFormat AVOutputFormat

目录

• AVInputFormat
  • 1. AVInputFormat是demuxer或者indev
  • 2. AVInputFormat的声明
  • 3. demuxer_list的定义位于libavformat/demuxer_list.c
  • 4.. indev_list的定义位于libavdevice/indev_list.c
• AVOutputFormat
  • 1. AVOutputFormat是muxer或者outdev
  • 2. AVOutputFormat的声明
  • 3. muxer_list的定义位于libavformat/muxer_list.c
  • 4. outdev_list的定义位于libavdevice/outdev_list.c
• 结论

AVInputFormat

1. AVInputFormat是demuxer或者indev

    AVInputFormat *previn = NULL, *in; 
    for (int i = 0; (in = (AVInputFormat*)demuxer_list[i]); i++) {
        if (previn)
            previn->next = in;
        previn = in;
    }
 
    if (indev_list) {
        for (int i = 0; (in = (AVInputFormat*)indev_list[i]); i++) {
            if (previn)
                previn->next = in;
            previn = in;
        }
    }

2. AVInputFormat的声明

typedef struct AVInputFormat {
    /**
     * A comma separated list of short names for the format. New names
     * may be appended with a minor bump.
     */
    const char *name;
 
    /**
     * Descriptive name for the format, meant to be more human-readable
     * than name. You should use the NULL_IF_CONFIG_SMALL() macro
     * to define it.
     */
    const char *long_name;
 
    /**
     * Can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_SHOW_IDS,
     * AVFMT_NOTIMESTAMPS, AVFMT_GENERIC_INDEX, AVFMT_TS_DISCONT, AVFMT_NOBINSEARCH,
     * AVFMT_NOGENSEARCH, AVFMT_NO_BYTE_SEEK, AVFMT_SEEK_TO_PTS.
     */
    int flags;
 
    /**
     * If extensions are defined, then no probe is done. You should
     * usually not use extension format guessing because it is not
     * reliable enough
     */
    const char *extensions;
 
    const struct AVCodecTag * const *codec_tag;
 
    const AVClass *priv_class; ///< AVClass for the private context
 
    /**
     * Comma-separated list of mime types.
     * It is used check for matching mime types while probing.
     * @see av_probe_input_format2
     */
    const char *mime_type;
 
    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    ff_const59 struct AVInputFormat *next;
 
    /**
     * Raw demuxers store their codec ID here.
     */
    int raw_codec_id;
 
    /**
     * Size of private data so that it can be allocated in the wrapper.
     */
    int priv_data_size;
 
    /**
     * Tell if a given file has a chance of being parsed as this format.
     * The buffer provided is guaranteed to be AVPROBE_PADDING_SIZE bytes
     * big so you do not have to check for that unless you need more.
     */
    int (*read_probe)(const AVProbeData *);
 
    /**
     * Read the format header and initialize the AVFormatContext
     * structure. Return 0 if OK. 'avformat_new_stream' should be
     * called to create new streams.
     */
    int (*read_header)(struct AVFormatContext *);
 
    /**
     * Read one packet and put it in 'pkt'. pts and flags are also
     * set. 'avformat_new_stream' can be called only if the flag
     * AVFMTCTX_NOHEADER is used and only in the calling thread (not in a
     * background thread).
     * @return 0 on success, < 0 on error.
     *         When returning an error, pkt must not have been allocated
     *         or must be freed before returning
     */
    int (*read_packet)(struct AVFormatContext *, AVPacket *pkt);
 
    /**
     * Close the stream. The AVFormatContext and AVStreams are not
     * freed by this function
     */
    int (*read_close)(struct AVFormatContext *);
 
    /**
     * Seek to a given timestamp relative to the frames in
     * stream component stream_index.
     * @param stream_index Must not be -1.
     * @param flags Selects which direction should be preferred if no exact
     *              match is available.
     * @return >= 0 on success (but not necessarily the new offset)
     */
    int (*read_seek)(struct AVFormatContext *,
                     int stream_index, int64_t timestamp, int flags);
 
    /**
     * Get the next timestamp in stream[stream_index].time_base units.
     * @return the timestamp or AV_NOPTS_VALUE if an error occurred
     */
    int64_t (*read_timestamp)(struct AVFormatContext *s, int stream_index,
                              int64_t *pos, int64_t pos_limit);
 
    /**
     * Start/resume playing - only meaningful if using a network-based format
     * (RTSP).
     */
    int (*read_play)(struct AVFormatContext *);
 
    /**
     * Pause playing - only meaningful if using a network-based format
     * (RTSP).
     */
    int (*read_pause)(struct AVFormatContext *);
 
    /**
     * Seek to timestamp ts.
     * Seeking will be done so that the point from which all active streams
     * can be presented successfully will be closest to ts and within min/max_ts.
     * Active streams are all streams that have AVStream.discard < AVDISCARD_ALL.
     */
    int (*read_seek2)(struct AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
 
    /**
     * Returns device list with it properties.
     * @see avdevice_list_devices() for more details.
     */
    int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
 
    /**
     * Initialize device capabilities submodule.
     * @see avdevice_capabilities_create() for more details.
     */
    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
 
    /**
     * Free device capabilities submodule.
     * @see avdevice_capabilities_free() for more details.
     */
    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
} AVInputFormat;
 
 
 

3. demuxer_list的定义位于libavformat/demuxer_list.c

static const AVInputFormat * const demuxer_list[] = {
    &ff_aa_demuxer,
    &ff_aac_demuxer,
    &ff_ac3_demuxer,
    &ff_acm_demuxer,
    &ff_act_demuxer,
    &ff_adf_demuxer,
    &ff_adp_demuxer,
    &ff_ads_demuxer,
    &ff_adx_demuxer,
    &ff_aea_demuxer,
    &ff_afc_demuxer,
    &ff_aiff_demuxer,
    &ff_aix_demuxer,
    &ff_amr_demuxer,
    &ff_amrnb_demuxer,
    &ff_amrwb_demuxer,
    &ff_anm_demuxer,
    &ff_apc_demuxer,
    &ff_ape_demuxer,
    &ff_apng_demuxer,
    &ff_aptx_demuxer,
    &ff_aptx_hd_demuxer,
    &ff_aqtitle_demuxer,
    &ff_asf_demuxer,
    &ff_asf_o_demuxer,
    &ff_ass_demuxer,
    &ff_ast_demuxer,
    &ff_au_demuxer,
    &ff_avi_demuxer,
    &ff_avr_demuxer,
    &ff_avs_demuxer,
    &ff_avs2_demuxer,
    &ff_bethsoftvid_demuxer,
    &ff_bfi_demuxer,
    &ff_bintext_demuxer,
    &ff_bink_demuxer,
    &ff_bit_demuxer,
    &ff_bmv_demuxer,
    &ff_bfstm_demuxer,
    &ff_brstm_demuxer,
    &ff_boa_demuxer,
    &ff_c93_demuxer,
    &ff_caf_demuxer,
    &ff_cavsvideo_demuxer,
    &ff_cdg_demuxer,
    &ff_cdxl_demuxer,
    &ff_cine_demuxer,
    &ff_codec2_demuxer,
    &ff_codec2raw_demuxer,
    &ff_concat_demuxer,
    &ff_data_demuxer,
    &ff_daud_demuxer,
    &ff_dcstr_demuxer,
    &ff_dfa_demuxer,
    &ff_dhav_demuxer,
    &ff_dirac_demuxer,
    &ff_dnxhd_demuxer,
    &ff_dsf_demuxer,
    &ff_dsicin_demuxer,
    &ff_dss_demuxer,
    &ff_dts_demuxer,
    &ff_dtshd_demuxer,
    &ff_dv_demuxer,
    &ff_dvbsub_demuxer,
    &ff_dvbtxt_demuxer,
    &ff_dxa_demuxer,
    &ff_ea_demuxer,
    &ff_ea_cdata_demuxer,
    &ff_eac3_demuxer,
    &ff_epaf_demuxer,
    &ff_ffmetadata_demuxer,
    &ff_filmstrip_demuxer,
    &ff_fits_demuxer,
    &ff_flac_demuxer,
    &ff_flic_demuxer,
    &ff_flv_demuxer,
    &ff_live_flv_demuxer,
    &ff_fourxm_demuxer,
    &ff_frm_demuxer,
    &ff_fsb_demuxer,
    &ff_g722_demuxer,
    &ff_g723_1_demuxer,
    &ff_g726_demuxer,
    &ff_g726le_demuxer,
    &ff_g729_demuxer,
    &ff_gdv_demuxer,
    &ff_genh_demuxer,
    &ff_gif_demuxer,
    &ff_gsm_demuxer,
    &ff_gxf_demuxer,
    &ff_h261_demuxer,
    &ff_h263_demuxer,
    &ff_h264_demuxer,
    &ff_hcom_demuxer,
    &ff_hevc_demuxer,
    &ff_hls_demuxer,
    &ff_hnm_demuxer,
    &ff_ico_demuxer,
    &ff_idcin_demuxer,
    &ff_idf_demuxer,
    &ff_iff_demuxer,
    &ff_ifv_demuxer,
    &ff_ilbc_demuxer,
    &ff_image2_demuxer,
    &ff_image2pipe_demuxer,
    &ff_image2_alias_pix_demuxer,
    &ff_image2_brender_pix_demuxer,
    &ff_ingenient_demuxer,
    &ff_ipmovie_demuxer,
    &ff_ircam_demuxer,
    &ff_iss_demuxer,
    &ff_iv8_demuxer,
    &ff_ivf_demuxer,
    &ff_ivr_demuxer,
    &ff_jacosub_demuxer,
    &ff_jv_demuxer,
    &ff_kux_demuxer,
    &ff_lmlm4_demuxer,
    &ff_loas_demuxer,
    &ff_lrc_demuxer,
    &ff_lvf_demuxer,
    &ff_lxf_demuxer,
    &ff_m4v_demuxer,
    &ff_matroska_demuxer,
    &ff_mgsts_demuxer,
    &ff_microdvd_demuxer,
    &ff_mjpeg_demuxer,
    &ff_mjpeg_2000_demuxer,
    &ff_mlp_demuxer,
    &ff_mlv_demuxer,
    &ff_mm_demuxer,
    &ff_mmf_demuxer,
    &ff_mov_demuxer,
    &ff_mp3_demuxer,
    &ff_mpc_demuxer,
    &ff_mpc8_demuxer,
    &ff_mpegps_demuxer,
    &ff_mpegts_demuxer,
    &ff_mpegtsraw_demuxer,
    &ff_mpegvideo_demuxer,
    &ff_mpjpeg_demuxer,
    &ff_mpl2_demuxer,
    &ff_mpsub_demuxer,
    &ff_msf_demuxer,
    &ff_msnwc_tcp_demuxer,
    &ff_mtaf_demuxer,
    &ff_mtv_demuxer,
    &ff_musx_demuxer,
    &ff_mv_demuxer,
    &ff_mvi_demuxer,
    &ff_mxf_demuxer,
    &ff_mxg_demuxer,
    &ff_nc_demuxer,
    &ff_nistsphere_demuxer,
    &ff_nsp_demuxer,
    &ff_nsv_demuxer,
    &ff_nut_demuxer,
    &ff_nuv_demuxer,
    &ff_ogg_demuxer,
    &ff_oma_demuxer,
    &ff_paf_demuxer,
    &ff_pcm_alaw_demuxer,
    &ff_pcm_mulaw_demuxer,
    &ff_pcm_vidc_demuxer,
    &ff_pcm_f64be_demuxer,
    &ff_pcm_f64le_demuxer,
    &ff_pcm_f32be_demuxer,
    &ff_pcm_f32le_demuxer,
    &ff_pcm_s32be_demuxer,
    &ff_pcm_s32le_demuxer,
    &ff_pcm_s24be_demuxer,
    &ff_pcm_s24le_demuxer,
    &ff_pcm_s16be_demuxer,
    &ff_pcm_s16le_demuxer,
    &ff_pcm_s8_demuxer,
    &ff_pcm_u32be_demuxer,
    &ff_pcm_u32le_demuxer,
    &ff_pcm_u24be_demuxer,
    &ff_pcm_u24le_demuxer,
    &ff_pcm_u16be_demuxer,
    &ff_pcm_u16le_demuxer,
    &ff_pcm_u8_demuxer,
    &ff_pjs_demuxer,
    &ff_pmp_demuxer,
    &ff_pva_demuxer,
    &ff_pvf_demuxer,
    &ff_qcp_demuxer,
    &ff_r3d_demuxer,
    &ff_rawvideo_demuxer,
    &ff_realtext_demuxer,
    &ff_redspark_demuxer,
    &ff_rl2_demuxer,
    &ff_rm_demuxer,
    &ff_roq_demuxer,
    &ff_rpl_demuxer,
    &ff_rsd_demuxer,
    &ff_rso_demuxer,
    &ff_rtp_demuxer,
    &ff_rtsp_demuxer,
    &ff_s337m_demuxer,
    &ff_sami_demuxer,
    &ff_sap_demuxer,
    &ff_sbc_demuxer,
    &ff_sbg_demuxer,
    &ff_scc_demuxer,
    &ff_sdp_demuxer,
    &ff_sdr2_demuxer,
    &ff_sds_demuxer,
    &ff_sdx_demuxer,
    &ff_segafilm_demuxer,
    &ff_ser_demuxer,
    &ff_shorten_demuxer,
    &ff_siff_demuxer,
    &ff_sln_demuxer,
    &ff_smacker_demuxer,
    &ff_smjpeg_demuxer,
    &ff_smush_demuxer,
    &ff_sol_demuxer,
    &ff_sox_demuxer,
    &ff_spdif_demuxer,
    &ff_srt_demuxer,
    &ff_str_demuxer,
    &ff_stl_demuxer,
    &ff_subviewer1_demuxer,
    &ff_subviewer_demuxer,
    &ff_sup_demuxer,
    &ff_svag_demuxer,
    &ff_swf_demuxer,
    &ff_tak_demuxer,
    &ff_tedcaptions_demuxer,
    &ff_thp_demuxer,
    &ff_threedostr_demuxer,
    &ff_tiertexseq_demuxer,
    &ff_tmv_demuxer,
    &ff_truehd_demuxer,
    &ff_tta_demuxer,
    &ff_txd_demuxer,
    &ff_tty_demuxer,
    &ff_ty_demuxer,
    &ff_v210_demuxer,
    &ff_v210x_demuxer,
    &ff_vag_demuxer,
    &ff_vc1_demuxer,
    &ff_vc1t_demuxer,
    &ff_vividas_demuxer,
    &ff_vivo_demuxer,
    &ff_vmd_demuxer,
    &ff_vobsub_demuxer,
    &ff_voc_demuxer,
    &ff_vpk_demuxer,
    &ff_vplayer_demuxer,
    &ff_vqf_demuxer,
    &ff_w64_demuxer,
    &ff_wav_demuxer,
    &ff_wc3_demuxer,
    &ff_webm_dash_manifest_demuxer,
    &ff_webvtt_demuxer,
    &ff_wsaud_demuxer,
    &ff_wsd_demuxer,
    &ff_wsvqa_demuxer,
    &ff_wtv_demuxer,
    &ff_wve_demuxer,
    &ff_wv_demuxer,
    &ff_xa_demuxer,
    &ff_xbin_demuxer,
    &ff_xmv_demuxer,
    &ff_xvag_demuxer,
    &ff_xwma_demuxer,
    &ff_yop_demuxer,
    &ff_yuv4mpegpipe_demuxer,
    &ff_image_bmp_pipe_demuxer,
    &ff_image_dds_pipe_demuxer,
    &ff_image_dpx_pipe_demuxer,
    &ff_image_exr_pipe_demuxer,
    &ff_image_gif_pipe_demuxer,
    &ff_image_j2k_pipe_demuxer,
    &ff_image_jpeg_pipe_demuxer,
    &ff_image_jpegls_pipe_demuxer,
    &ff_image_pam_pipe_demuxer,
    &ff_image_pbm_pipe_demuxer,
    &ff_image_pcx_pipe_demuxer,
    &ff_image_pgmyuv_pipe_demuxer,
    &ff_image_pgm_pipe_demuxer,
    &ff_image_pictor_pipe_demuxer,
    &ff_image_png_pipe_demuxer,
    &ff_image_ppm_pipe_demuxer,
    &ff_image_psd_pipe_demuxer,
    &ff_image_qdraw_pipe_demuxer,
    &ff_image_sgi_pipe_demuxer,
    &ff_image_svg_pipe_demuxer,
    &ff_image_sunrast_pipe_demuxer,
    &ff_image_tiff_pipe_demuxer,
    &ff_image_webp_pipe_demuxer,
    &ff_image_xpm_pipe_demuxer,
    &ff_image_xwd_pipe_demuxer,
    NULL };
 
 
// 举例说明
 
 
AVInputFormat ff_aac_demuxer = {
    .name         = "aac",
    .long_name    = NULL_IF_CONFIG_SMALL("raw ADTS AAC (Advanced Audio Coding)"),
    .read_probe   = adts_aac_probe,
    .read_header  = adts_aac_read_header,
    .read_packet  = adts_aac_read_packet,
    .flags        = AVFMT_GENERIC_INDEX,
    .extensions   = "aac",
    .mime_type    = "audio/aac,audio/aacp,audio/x-aac",
    .raw_codec_id = AV_CODEC_ID_AAC,
};

4.. indev_list的定义位于libavdevice/indev_list.c

static const AVInputFormat * const indev_list[] = {
    &ff_alsa_demuxer,
    &ff_fbdev_demuxer,
    &ff_lavfi_demuxer,
    &ff_oss_demuxer,
    &ff_sndio_demuxer,
    &ff_v4l2_demuxer,
    &ff_xcbgrab_demuxer,
    NULL 
};
 
// 举例说明
AVInputFormat ff_lavfi_demuxer = {
    .name           = "lavfi",
    .long_name      = NULL_IF_CONFIG_SMALL("Libavfilter virtual input device"),
    .priv_data_size = sizeof(LavfiContext),
    .read_header    = lavfi_read_header,
    .read_packet    = lavfi_read_packet,
    .read_close     = lavfi_read_close,
    .flags          = AVFMT_NOFILE,
    .priv_class     = &lavfi_class,
};

AVOutputFormat

1. AVOutputFormat是muxer或者outdev

    AVOutputFormat *prevout = NULL, *out;
    for (int i = 0; (out = (AVOutputFormat*)muxer_list[i]); i++) {
        if (prevout)
            prevout->next = out;
        prevout = out;
    }
 
    if (outdev_list) {
        for (int i = 0; (out = (AVOutputFormat*)outdev_list[i]); i++) {
            if (prevout)
                prevout->next = out;
            prevout = out;
        }
    }

2. AVOutputFormat的声明

typedef struct AVOutputFormat {
    const char *name;
    /**
     * Descriptive name for the format, meant to be more human-readable
     * than name. You should use the NULL_IF_CONFIG_SMALL() macro
     * to define it.
     */
    const char *long_name;
    const char *mime_type;
    const char *extensions; /**< comma-separated filename extensions */
    /* output support */
    enum AVCodecID audio_codec;    /**< default audio codec */
    enum AVCodecID video_codec;    /**< default video codec */
    enum AVCodecID subtitle_codec; /**< default subtitle codec */
    /**
     * can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER,
     * AVFMT_GLOBALHEADER, AVFMT_NOTIMESTAMPS, AVFMT_VARIABLE_FPS,
     * AVFMT_NODIMENSIONS, AVFMT_NOSTREAMS, AVFMT_ALLOW_FLUSH,
     * AVFMT_TS_NONSTRICT, AVFMT_TS_NEGATIVE
     */
    int flags;
 
    /**
     * List of supported codec_id-codec_tag pairs, ordered by "better
     * choice first". The arrays are all terminated by AV_CODEC_ID_NONE.
     */
    const struct AVCodecTag * const *codec_tag;
 
 
    const AVClass *priv_class; ///< AVClass for the private context
 
    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    /**
     * The ff_const59 define is not part of the public API and will
     * be removed without further warning.
     */
#if FF_API_AVIOFORMAT
#define ff_const59
#else
#define ff_const59 const
#endif
    ff_const59 struct AVOutputFormat *next;
    /**
     * size of private data so that it can be allocated in the wrapper
     */
    int priv_data_size;
 
    int (*write_header)(struct AVFormatContext *);
    /**
     * Write a packet. If AVFMT_ALLOW_FLUSH is set in flags,
     * pkt can be NULL in order to flush data buffered in the muxer.
     * When flushing, return 0 if there still is more data to flush,
     * or 1 if everything was flushed and there is no more buffered
     * data.
     */
    int (*write_packet)(struct AVFormatContext *, AVPacket *pkt);
    int (*write_trailer)(struct AVFormatContext *);
    /**
     * Currently only used to set pixel format if not YUV420P.
     */
    int (*interleave_packet)(struct AVFormatContext *, AVPacket *out,
                             AVPacket *in, int flush);
    /**
     * Test if the given codec can be stored in this container.
     *
     * @return 1 if the codec is supported, 0 if it is not.
     *         A negative number if unknown.
     *         MKTAG('A', 'P', 'I', 'C') if the codec is only supported as AV_DISPOSITION_ATTACHED_PIC
     */
    int (*query_codec)(enum AVCodecID id, int std_compliance);
 
    void (*get_output_timestamp)(struct AVFormatContext *s, int stream,
                                 int64_t *dts, int64_t *wall);
    /**
     * Allows sending messages from application to device.
     */
    int (*control_message)(struct AVFormatContext *s, int type,
                           void *data, size_t data_size);
 
    /**
     * Write an uncoded AVFrame.
     *
     * See av_write_uncoded_frame() for details.
     *
     * The library will free *frame afterwards, but the muxer can prevent it
     * by setting the pointer to NULL.
     */
    int (*write_uncoded_frame)(struct AVFormatContext *, int stream_index,
                               AVFrame **frame, unsigned flags);
    /**
     * Returns device list with it properties.
     * @see avdevice_list_devices() for more details.
     */
    int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
    /**
     * Initialize device capabilities submodule.
     * @see avdevice_capabilities_create() for more details.
     */
    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
    /**
     * Free device capabilities submodule.
     * @see avdevice_capabilities_free() for more details.
     */
    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
    enum AVCodecID data_codec; /**< default data codec */
    /**
     * Initialize format. May allocate data here, and set any AVFormatContext or
     * AVStream parameters that need to be set before packets are sent.
     * This method must not write output.
     *
     * Return 0 if streams were fully configured, 1 if not, negative AVERROR on failure
     *
     * Any allocations made here must be freed in deinit().
     */
    int (*init)(struct AVFormatContext *);
    /**
     * Deinitialize format. If present, this is called whenever the muxer is being
     * destroyed, regardless of whether or not the header has been written.
     *
     * If a trailer is being written, this is called after write_trailer().
     *
     * This is called if init() fails as well.
     */
    void (*deinit)(struct AVFormatContext *);
    /**
     * Set up any necessary bitstream filtering and extract any extra data needed
     * for the global header.
     * Return 0 if more packets from this stream must be checked; 1 if not.
     */
    int (*check_bitstream)(struct AVFormatContext *, const AVPacket *pkt);
} AVOutputFormat;

3. muxer_list的定义位于libavformat/muxer_list.c

static const AVOutputFormat * const muxer_list[] = {
    &ff_a64_muxer,
    &ff_ac3_muxer,
    &ff_adts_muxer,
    &ff_adx_muxer,
    &ff_aiff_muxer,
    &ff_amr_muxer,
    &ff_apng_muxer,
    &ff_aptx_muxer,
    &ff_aptx_hd_muxer,
    &ff_asf_muxer,
    &ff_ass_muxer,
    &ff_ast_muxer,
    &ff_asf_stream_muxer,
    &ff_au_muxer,
    &ff_avi_muxer,
    &ff_avm2_muxer,
    &ff_avs2_muxer,
    &ff_bit_muxer,
    &ff_caf_muxer,
    &ff_cavsvideo_muxer,
    &ff_codec2_muxer,
    &ff_codec2raw_muxer,
    &ff_crc_muxer,
    &ff_dash_muxer,
    &ff_data_muxer,
    &ff_daud_muxer,
    &ff_dirac_muxer,
    &ff_dnxhd_muxer,
    &ff_dts_muxer,
    &ff_dv_muxer,
    &ff_eac3_muxer,
    &ff_f4v_muxer,
    &ff_ffmetadata_muxer,
    &ff_fifo_muxer,
    &ff_fifo_test_muxer,
    &ff_filmstrip_muxer,
    &ff_fits_muxer,
    &ff_flac_muxer,
    &ff_flv_muxer,
    &ff_framecrc_muxer,
    &ff_framehash_muxer,
    &ff_framemd5_muxer,
    &ff_g722_muxer,
    &ff_g723_1_muxer,
    &ff_g726_muxer,
    &ff_g726le_muxer,
    &ff_gif_muxer,
    &ff_gsm_muxer,
    &ff_gxf_muxer,
    &ff_h261_muxer,
    &ff_h263_muxer,
    &ff_h264_muxer,
    &ff_hash_muxer,
    &ff_hds_muxer,
    &ff_hevc_muxer,
    &ff_hls_muxer,
    &ff_ico_muxer,
    &ff_ilbc_muxer,
    &ff_image2_muxer,
    &ff_image2pipe_muxer,
    &ff_ipod_muxer,
    &ff_ircam_muxer,
    &ff_ismv_muxer,
    &ff_ivf_muxer,
    &ff_jacosub_muxer,
    &ff_latm_muxer,
    &ff_lrc_muxer,
    &ff_m4v_muxer,
    &ff_md5_muxer,
    &ff_matroska_muxer,
    &ff_matroska_audio_muxer,
    &ff_microdvd_muxer,
    &ff_mjpeg_muxer,
    &ff_mlp_muxer,
    &ff_mmf_muxer,
    &ff_mov_muxer,
    &ff_mp2_muxer,
    &ff_mp3_muxer,
    &ff_mp4_muxer,
    &ff_mpeg1system_muxer,
    &ff_mpeg1vcd_muxer,
    &ff_mpeg1video_muxer,
    &ff_mpeg2dvd_muxer,
    &ff_mpeg2svcd_muxer,
    &ff_mpeg2video_muxer,
    &ff_mpeg2vob_muxer,
    &ff_mpegts_muxer,
    &ff_mpjpeg_muxer,
    &ff_mxf_muxer,
    &ff_mxf_d10_muxer,
    &ff_mxf_opatom_muxer,
    &ff_null_muxer,
    &ff_nut_muxer,
    &ff_oga_muxer,
    &ff_ogg_muxer,
    &ff_ogv_muxer,
    &ff_oma_muxer,
    &ff_opus_muxer,
    &ff_pcm_alaw_muxer,
    &ff_pcm_mulaw_muxer,
    &ff_pcm_vidc_muxer,
    &ff_pcm_f64be_muxer,
    &ff_pcm_f64le_muxer,
    &ff_pcm_f32be_muxer,
    &ff_pcm_f32le_muxer,
    &ff_pcm_s32be_muxer,
    &ff_pcm_s32le_muxer,
    &ff_pcm_s24be_muxer,
    &ff_pcm_s24le_muxer,
    &ff_pcm_s16be_muxer,
    &ff_pcm_s16le_muxer,
    &ff_pcm_s8_muxer,
    &ff_pcm_u32be_muxer,
    &ff_pcm_u32le_muxer,
    &ff_pcm_u24be_muxer,
    &ff_pcm_u24le_muxer,
    &ff_pcm_u16be_muxer,
    &ff_pcm_u16le_muxer,
    &ff_pcm_u8_muxer,
    &ff_psp_muxer,
    &ff_rawvideo_muxer,
    &ff_rm_muxer,
    &ff_roq_muxer,
    &ff_rso_muxer,
    &ff_rtp_muxer,
    &ff_rtp_mpegts_muxer,
    &ff_rtsp_muxer,
    &ff_sap_muxer,
    &ff_sbc_muxer,
    &ff_scc_muxer,
    &ff_segafilm_muxer,
    &ff_segment_muxer,
    &ff_stream_segment_muxer,
    &ff_singlejpeg_muxer,
    &ff_smjpeg_muxer,
    &ff_smoothstreaming_muxer,
    &ff_sox_muxer,
    &ff_spx_muxer,
    &ff_spdif_muxer,
    &ff_srt_muxer,
    &ff_sup_muxer,
    &ff_swf_muxer,
    &ff_tee_muxer,
    &ff_tg2_muxer,
    &ff_tgp_muxer,
    &ff_mkvtimestamp_v2_muxer,
    &ff_truehd_muxer,
    &ff_tta_muxer,
    &ff_uncodedframecrc_muxer,
    &ff_vc1_muxer,
    &ff_vc1t_muxer,
    &ff_voc_muxer,
    &ff_w64_muxer,
    &ff_wav_muxer,
    &ff_webm_muxer,
    &ff_webm_dash_manifest_muxer,
    &ff_webm_chunk_muxer,
    &ff_webp_muxer,
    &ff_webvtt_muxer,
    &ff_wtv_muxer,
    &ff_wv_muxer,
    &ff_yuv4mpegpipe_muxer,
    NULL };
 
// 举例说明
AVOutputFormat ff_h264_muxer = {
    .name              = "h264",
    .long_name         = NULL_IF_CONFIG_SMALL("raw H.264 video"),
    .extensions        = "h264,264",
    .audio_codec       = AV_CODEC_ID_NONE,
    .video_codec       = AV_CODEC_ID_H264,
    .write_header      = force_one_stream,
    .write_packet      = ff_raw_write_packet,
    .check_bitstream   = h264_check_bitstream,
    .flags             = AVFMT_NOTIMESTAMPS,
};

4. outdev_list的定义位于libavdevice/outdev_list.c

static const AVOutputFormat * const outdev_list[] = {
    &ff_alsa_muxer,
    &ff_fbdev_muxer,
    &ff_oss_muxer,
    &ff_sdl2_muxer,
    &ff_sndio_muxer,
    &ff_v4l2_muxer,
    &ff_xv_muxer,
    NULL 
};
 
AVOutputFormat ff_sdl2_muxer = {
    .name           = "sdl,sdl2",
    .long_name      = NULL_IF_CONFIG_SMALL("SDL2 output device"),
    .priv_data_size = sizeof(SDLContext),
    .audio_codec    = AV_CODEC_ID_NONE,
    .video_codec    = AV_CODEC_ID_RAWVIDEO,
    .write_header   = sdl2_write_header,
    .write_packet   = sdl2_write_packet,
    .write_trailer  = sdl2_write_trailer,
    .flags          = AVFMT_NOFILE | AVFMT_VARIABLE_FPS | AVFMT_NOTIMESTAMPS,
    .priv_class     = &sdl2_class,
};
 

结论

AVInputFormat可以理解为demuxer, AVOutputFormat可以理解为muxer