[FFmpeg-devel] Re: [PATCH] libavformat/rot: added rot pcm header support

[Michael Niedermayer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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Hi

On Fri, Jan 23, 2026 at 01:35:29PM +0100, 9mmilly via ffmpeg-devel wrote:
[...]
> diff --git a/libavformat/rot.c b/libavformat/rot.c
> new file mode 100644
> index 0000000000..520f038f8b
> --- /dev/null
> +++ b/libavformat/rot.c
> @@ -0,0 +1,230 @@
> +/*
> +* Copyright (c) 2014 9mmilly
> +*
> +* This file is part of FFmpeg.
> +*
> +* Permission to use, copy, modify, and/or distribute this software for any
> +* purpose with or without fee is hereby granted, provided that the above
> +* copyright notice and this permission notice appear in all copies.
> +*
> +* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
> +* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
> +* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
> +* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
> +* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
> +* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
> +* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
> +*/
> +
> +#include <stdint.h>
> +#include <string.h>
> +
> +#include "avformat.h"
> +#include "demux.h"
> +#include "internal.h"
> +#include "libavcodec/codec_id.h"
> +#include "mux.h"
> +#include "pcm.h"
> +#include "rawenc.h"
> +
> +#define ROT_IDENTIFIER "frot"
> +
> +typedef enum {
> +    ROT_FORMAT_S8,
> +    ROT_FORMAT_S16,
> +    ROT_FORMAT_S24,
> +    ROT_FORMAT_S32,
> +    ROT_FORMAT_FLOAT,
> +    ROT_FORMAT_DOUBLE
> +} rot_format;
> +
> +/* demuxer */
> +

> +static int rot_probe(const AVProbeData *probe) {
> +    if (probe->buf_size <= 32)
> +        return 0;
> +
> +    if (probe->buf_size >= 36) {
> +        if (memcmp(probe->buf, ROT_IDENTIFIER, 4) == 0)
> +            return AVPROBE_SCORE_MAX;
> +    }
> +    return 0;
> +}

the probe->buf_size <= 32 block is redundant



> +
> +static int rot_read_header(AVFormatContext *context) {
> +    uint8_t header_buffer[8];
> +
> +    if (avio_read(context->pb, header_buffer, sizeof(header_buffer)) != 8)
> +        return AVERROR_INVALIDDATA;
> +

> +    uint16_t sample_rate;
> +    memcpy(&sample_rate, (header_buffer + 4), 2);

will fail on big endian


> +
> +    uint8_t channels;
> +    memcpy(&channels, (header_buffer + 6), 1);
> +
> +    uint8_t format;
> +    memcpy(&format, (header_buffer + 7), 1);
> +
> +    if (sample_rate <= 0 || channels <= 0)
> +        return AVERROR_INVALIDDATA;
> +
> +    AVStream *stream = avformat_new_stream(context, NULL);
> +    if (!stream) {
> +        av_log(stream, AV_LOG_ERROR, "invalid audio parameters\n");
> +        return AVERROR(ENOMEM);
> +    }
> +
> +    stream->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
> +    stream->codecpar->ch_layout.nb_channels = channels;
> +    stream->codecpar->sample_rate = sample_rate;
> +

> +    switch (format) {
> +    case ROT_FORMAT_S8:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_S8;
> +        stream->codecpar->bits_per_coded_sample = 8;
> +        stream->codecpar->block_align = 8 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 8;
> +        break;
> +
> +    case ROT_FORMAT_S16:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_S16LE;
> +        stream->codecpar->bits_per_coded_sample = 16;
> +        stream->codecpar->block_align = 16 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 16;
> +        break;
> +
> +    case ROT_FORMAT_S24:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_S24LE;
> +        stream->codecpar->bits_per_coded_sample = 24;
> +        stream->codecpar->block_align = 24 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 24;
> +        break;
> +
> +    case ROT_FORMAT_S32:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_S32LE;
> +        stream->codecpar->bits_per_coded_sample = 32;
> +        stream->codecpar->block_align = 32 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 32;
> +        break;
> +
> +    case ROT_FORMAT_FLOAT:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_F32LE;
> +        stream->codecpar->bits_per_coded_sample = 32;
> +        stream->codecpar->block_align = 32 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 32;
> +        break;
> +
> +    case ROT_FORMAT_DOUBLE:
> +        stream->codecpar->codec_id = AV_CODEC_ID_PCM_F64LE;
> +        stream->codecpar->bits_per_coded_sample = 64;
> +        stream->codecpar->block_align = 64 * channels / 8;
> +        stream->codecpar->bit_rate = (int64_t)sample_rate * channels * 64;
> +        break;

the computation of block_align and bit_rate can be factored out using
bits_per_coded_sample


> +
> +    default:
> +        return AVERROR_INVALIDDATA;
> +    }
> +    avpriv_set_pts_info(stream, 64, 1, sample_rate);
> +
> +    return 0;
> +}
> +
> +const FFInputFormat ff_rot_demuxer = {
> +    .p.name = "rot",
> +    .p.long_name = NULL_IF_CONFIG_SMALL("rot pcm header"),
> +    .priv_data_size = 0,
> +    .p.extensions = "rot",
> +    .read_probe = rot_probe,
> +    .read_header = rot_read_header,
> +    .read_packet = ff_pcm_read_packet};
> +

> +/* muxer */
> +
> +static int rot_write_header(AVFormatContext *context) {

its probably cleaner to have this in a seperate file

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 

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