[FFmpeg-devel] [PATCH] doc/examples: add avio_writing examples
Nicolas George
george at nsup.org
Thu Nov 6 20:45:53 CET 2014
Le quintidi 15 brumaire, an CCXXIII, Stefano Sabatini a écrit :
> Show how to use the AVIO writing API.
> ---
> .gitignore | 1 +
> configure | 1 +
> doc/examples/Makefile | 1 +
> doc/examples/avio_writing.c | 225 ++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 228 insertions(+)
> create mode 100644 doc/examples/avio_writing.c
>
> diff --git a/.gitignore b/.gitignore
> index 793d33a..628ffb1 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -37,6 +37,7 @@
> /doc/avoptions_format.texi
> /doc/doxy/html/
> /doc/examples/avio_reading
> +/doc/examples/avio_writing
> /doc/examples/decoding_encoding
> /doc/examples/demuxing_decoding
> /doc/examples/extract_mvs
> diff --git a/configure b/configure
> index 570878d..5b3a246 100755
> --- a/configure
> +++ b/configure
> @@ -1310,6 +1310,7 @@ COMPONENT_LIST="
>
> EXAMPLE_LIST="
> avio_reading_example
> + avio_writing_example
> decoding_encoding_example
> demuxing_decoding_example
> extract_mvs_example
> diff --git a/doc/examples/Makefile b/doc/examples/Makefile
> index 07251fe..ad10b5b 100644
> --- a/doc/examples/Makefile
> +++ b/doc/examples/Makefile
> @@ -12,6 +12,7 @@ CFLAGS := $(shell pkg-config --cflags $(FFMPEG_LIBS)) $(CFLAGS)
> LDLIBS := $(shell pkg-config --libs $(FFMPEG_LIBS)) $(LDLIBS)
>
> EXAMPLES= avio_reading \
> + avio_writing \
> decoding_encoding \
> demuxing_decoding \
> extract_mvs \
> diff --git a/doc/examples/avio_writing.c b/doc/examples/avio_writing.c
> new file mode 100644
> index 0000000..27ef21a
> --- /dev/null
> +++ b/doc/examples/avio_writing.c
> @@ -0,0 +1,225 @@
> +/*
> + * Copyright (c) 2014 Stefano Sabatini
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +/**
> + * @file
> + * libavformat AVIOContext API example.
> + *
> + * Make libavformat demuxer access media content through a custom
s/demuxer/muxer/?
> + * AVIOContext write callback.
> + * @example avio_writing.c
> + */
> +
> +#include <libavcodec/avcodec.h>
> +#include <libavformat/avformat.h>
> +#include <libavformat/avio.h>
> +#include <libavutil/file.h>
> +#include <libavutil/timestamp.h>
> +
> +struct buffer_data {
> + uint8_t *buf;
> + size_t size;
> + uint8_t *ptr;
> + size_t room; ///< size left in the buffer
> +};
> +
> +static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag)
> +{
> + AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
> +
> + printf("%s: pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
> + tag,
> + av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
> + av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
> + av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
> + pkt->stream_index);
> +}
Is it really useful for the example?
> +
> +static int write_packet(void *opaque, uint8_t *buf, int buf_size)
> +{
> + struct buffer_data *bd = (struct buffer_data *)opaque;
> + while (buf_size > bd->room) {
> + int64_t offset = bd->ptr - bd->buf;
> + bd->buf = av_realloc_f(bd->buf, 2, bd->size);
> + if (!bd->buf)
> + return AVERROR(ENOMEM);
> + bd->size *= 2;
> + bd->ptr = bd->buf + offset;
> + bd->room = bd->size - offset;
> + }
> + printf("write packet pkt_size:%d used_buf_size:%zu buf_size:%zu buf_room:%zu\n", buf_size, bd->ptr-bd->buf, bd->size, bd->room);
> +
> + /* copy buffer data to buffer_data buffer */
> + memcpy(bd->ptr, buf, buf_size);
> + bd->ptr += buf_size;
> + bd->room -= buf_size;
> +
> + return buf_size;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + AVFormatContext *ifmt_ctx = NULL;
> + AVFormatContext *ofmt_ctx = NULL;
> + AVIOContext *avio_ctx = NULL;
> + uint8_t *avio_ctx_buffer = NULL;
> + size_t avio_ctx_buffer_size = 4096;
> + char *in_filename = NULL;
> + char *out_filename = NULL;
> + int i, ret = 0;
> + struct buffer_data bd = { 0 };
> + const size_t bd_buf_size = 1024;
> + AVPacket pkt;
> +
> + if (argc != 3) {
> + fprintf(stderr, "usage: %s input_file output_file\n"
> + "API example program to show how to write to a custom buffer "
> + "accessed through AVIOContext.\n"
> + "Remux the content of input_file to output_file, writing to a custom buffer.\n"
> + "The output file must support the same codec as the input file.\n", argv[0]);
> + return 1;
> + }
The input part, is it really necessary for the usefulness of the example? We
already have demuxing examples and muxing examples, so I think an example
about custom AVIO contexts could be underdeveloped in that regard: just
write synthetic sound to a WAVE file or something.
> + in_filename = argv[1];
> + out_filename = argv[2];
> +
> + av_register_all();
> +
> + if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
> + fprintf(stderr, "Could not open input file '%s'", in_filename);
> + goto end;
> + }
> +
> + if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
> + fprintf(stderr, "Failed to retrieve input stream information");
> + goto end;
> + }
> +
> + av_dump_format(ifmt_ctx, 0, in_filename, 0);
> +
> + /* fill opaque structure used by the AVIOContext write callback */
> + bd.ptr = bd.buf = av_malloc(bd_buf_size);
> + if (!bd.buf) {
> + ret = AVERROR(ENOMEM);
> + goto end;
> + }
> + bd.size = bd.room = bd_buf_size;
> +
> + avio_ctx_buffer = av_malloc(avio_ctx_buffer_size);
> + if (!avio_ctx_buffer) {
> + ret = AVERROR(ENOMEM);
> + goto end;
> + }
> + avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,
> + 1, &bd, NULL, &write_packet, NULL);
> + if (!avio_ctx) {
> + ret = AVERROR(ENOMEM);
> + goto end;
> + }
> +
> + ret = avformat_alloc_output_context2(&ofmt_ctx, NULL, "mpegts", NULL);
> + if (ret < 0) {
> + fprintf(stderr, "Could not create output context\n");
> + goto end;
> + }
> + ofmt_ctx->pb = avio_ctx;
> +
> + for (i = 0; i < ifmt_ctx->nb_streams; i++) {
> + AVStream *in_stream = ifmt_ctx->streams[i];
> + AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
> + if (!out_stream) {
> + fprintf(stderr, "Failed creating output stream\n");
> + ret = AVERROR_UNKNOWN;
> + goto end;
> + }
> +
> + ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
> + if (ret < 0) {
> + fprintf(stderr, "Failed to copy context from input to output stream codec context\n");
> + goto end;
> + }
> + out_stream->codec->codec_tag = 0;
> + if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
> + out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
> + }
> + av_dump_format(ofmt_ctx, 0, out_filename, 1);
> +
> + ret = avformat_write_header(ofmt_ctx, NULL);
> + if (ret < 0) {
> + fprintf(stderr, "Error occurred when opening output file\n");
> + goto end;
> + }
> +
> + while (1) {
> + AVStream *in_stream, *out_stream;
> +
> + ret = av_read_frame(ifmt_ctx, &pkt);
> + if (ret < 0)
> + break;
> +
> + in_stream = ifmt_ctx->streams[pkt.stream_index];
> + out_stream = ofmt_ctx->streams[pkt.stream_index];
> + log_packet(ifmt_ctx, &pkt, "in");
> +
> + /* copy packet */
> + av_packet_rescale_ts(&pkt, in_stream->time_base, out_stream->time_base);
> + pkt.pos = -1;
> + log_packet(ofmt_ctx, &pkt, "out");
> +
> + ret = av_interleaved_write_frame(ofmt_ctx, &pkt);
> + if (ret < 0) {
> + fprintf(stderr, "Error muxing packet\n");
> + break;
> + }
> + av_free_packet(&pkt);
> + }
> +
> + av_write_trailer(ofmt_ctx);
> +end:
> +
> + avformat_close_input(&ifmt_ctx);
> +
> + /* close output */
> + avformat_free_context(ofmt_ctx);
> + av_freep(&avio_ctx->buffer);
> + av_free(avio_ctx);
> +
> + /* write buffer to file */
> + {
> + FILE *out_file = fopen(out_filename, "w");
> + if (!out_file) {
> + fprintf(stderr, "Could not open file '%s'\n", out_filename);
> + ret = AVERROR(errno);
> + } else {
> + fwrite(bd.buf, bd.size, 1, out_file);
> + fclose(out_file);
> + }
> + }
> +
> + av_free(bd.buf);
> +
> + if (ret < 0 && ret != AVERROR_EOF) {
> + fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
> + return 1;
> + }
> +
> + return 0;
> +}
Regards,
--
Nicolas George
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