[FFmpeg-devel] [PATCH v2] avcodec/bsf: restructure the internal implementation of the bistream filter API
James Almer
jamrial at gmail.com
Sun Apr 19 19:42:37 EEST 2020
On 4/19/2020 1:01 PM, Marton Balint wrote:
>
>
> On Sun, 19 Apr 2020, James Almer wrote:
>
>> Process input data as soon as it's fed to av_bsf_send_packet(),
>> instead of
>> storing a single packet and expecting the user to call
>> av_bsf_receive_packet()
>> in order to trigger the decoding process before they are allowed to
>> feed more
>> data.
>>
>> This puts the bsf API more in line with the decoupled decode API, without
>> breaking existing using it.
>
> Well, previously it was assumed that av_bsf_send_packet() is never
> returning AVERROR_INVALIDDATA, that is no longer the case. That matters
> because current code in mux.c ingnores av_bsf_receive_packet() errors
> but not av_bsf_send_packet() errors.
The doxy states av_bsf_send_packet() can return an error, even if up
till now it hasn't.
Also, as i stated in the addendum below the Signed-off line, current
users following the recommended API usage (one call to
av_bsf_send_packet(), then several to av_bsf_receive_packet()) will see
no changes at all. So if you did that and expected no errors from
av_bsf_send_packet() in your mux.c code, you'll still get none.
>
> Unless there is some benefit I am not seeing, I'd rather keep things as
> is. Sorry.
The benefit is relaxing the current constrains of the API for new users
(including mux.c if you want to take advantage of it), but for those
that don't care about it, there's no difference at all. So any existing
code is in no risk of being broken.
>
> Regards,
> Marton
>
>
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>> Now without creating a new reference for the input packet, and
>> behaving the
>> exact same as before for current users that were following the doxy
>> right down
>> to the letter.
>>
>> Also didn't rename buffer_pkt to reduce the size of the diff and
>> easily find
>> the actual changes and additions.
>>
>> libavcodec/avcodec.h | 6 +-----
>> libavcodec/bsf.c | 42 +++++++++++++++++++++++++++++++-----------
>> 2 files changed, 32 insertions(+), 16 deletions(-)
>>
>> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
>> index b79b025e53..af2a1b0e90 100644
>> --- a/libavcodec/avcodec.h
>> +++ b/libavcodec/avcodec.h
>> @@ -4735,10 +4735,6 @@ int av_bsf_init(AVBSFContext *ctx);
>> /**
>> * Submit a packet for filtering.
>> *
>> - * After sending each packet, the filter must be completely drained
>> by calling
>> - * av_bsf_receive_packet() repeatedly until it returns
>> AVERROR(EAGAIN) or
>> - * AVERROR_EOF.
>> - *
>> * @param pkt the packet to filter. The bitstream filter will take
>> ownership of
>> * the packet and reset the contents of pkt. pkt is not touched if an
>> error occurs.
>> * If pkt is empty (i.e. NULL, or pkt->data is NULL and
>> pkt->side_data_elems zero),
>> @@ -4770,7 +4766,7 @@ int av_bsf_send_packet(AVBSFContext *ctx,
>> AVPacket *pkt);
>> * an error occurs.
>> *
>> * @note one input packet may result in several output packets, so
>> after sending
>> - * a packet with av_bsf_send_packet(), this function needs to be called
>> + * a packet with av_bsf_send_packet(), this function may need to be
>> called
>> * repeatedly until it stops returning 0. It is also possible for a
>> filter to
>> * output fewer packets than were sent to it, so this function may return
>> * AVERROR(EAGAIN) immediately after a successful av_bsf_send_packet()
>> call.
>> diff --git a/libavcodec/bsf.c b/libavcodec/bsf.c
>> index b9fc771a88..c79a8ebbdf 100644
>> --- a/libavcodec/bsf.c
>> +++ b/libavcodec/bsf.c
>> @@ -30,6 +30,7 @@
>>
>> struct AVBSFInternal {
>> AVPacket *buffer_pkt;
>> + AVPacket *out_pkt;
>> int eof;
>> };
>>
>> @@ -46,8 +47,10 @@ void av_bsf_free(AVBSFContext **pctx)
>> if (ctx->filter->priv_class && ctx->priv_data)
>> av_opt_free(ctx->priv_data);
>>
>> - if (ctx->internal)
>> + if (ctx->internal) {
>> av_packet_free(&ctx->internal->buffer_pkt);
>> + av_packet_free(&ctx->internal->out_pkt);
>> + }
>> av_freep(&ctx->internal);
>> av_freep(&ctx->priv_data);
>>
>> @@ -112,7 +115,8 @@ int av_bsf_alloc(const AVBitStreamFilter *filter,
>> AVBSFContext **pctx)
>> ctx->internal = bsfi;
>>
>> bsfi->buffer_pkt = av_packet_alloc();
>> - if (!bsfi->buffer_pkt) {
>> + bsfi->out_pkt = av_packet_alloc();
>> + if (!bsfi->buffer_pkt || !bsfi->out_pkt) {
>> ret = AVERROR(ENOMEM);
>> goto fail;
>> }
>> @@ -185,6 +189,7 @@ void av_bsf_flush(AVBSFContext *ctx)
>> bsfi->eof = 0;
>>
>> av_packet_unref(bsfi->buffer_pkt);
>> + av_packet_unref(bsfi->out_pkt);
>>
>> if (ctx->filter->flush)
>> ctx->filter->flush(ctx);
>> @@ -205,10 +210,21 @@ int av_bsf_send_packet(AVBSFContext *ctx,
>> AVPacket *pkt)
>> return AVERROR(EINVAL);
>> }
>>
>> + if (!bsfi->buffer_pkt->data &&
>> + !bsfi->buffer_pkt->side_data_elems)
>> + goto end;
>> +
>> + if (!bsfi->out_pkt->data && !bsfi->out_pkt->side_data_elems) {
>> + ret = ctx->filter->filter(ctx, bsfi->out_pkt);
>> + if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
>> + return ret;
>> + }
>> +
>> if (bsfi->buffer_pkt->data ||
>> bsfi->buffer_pkt->side_data_elems)
>> return AVERROR(EAGAIN);
>>
>> +end:
>> ret = av_packet_make_refcounted(pkt);
>> if (ret < 0)
>> return ret;
>> @@ -219,7 +235,17 @@ int av_bsf_send_packet(AVBSFContext *ctx,
>> AVPacket *pkt)
>>
>> int av_bsf_receive_packet(AVBSFContext *ctx, AVPacket *pkt)
>> {
>> - return ctx->filter->filter(ctx, pkt);
>> + AVBSFInternal *bsfi = ctx->internal;
>> + int ret;
>> +
>> + if (!bsfi->out_pkt->data && !bsfi->out_pkt->side_data_elems) {
>> + ret = ctx->filter->filter(ctx, bsfi->out_pkt);
>> + if (ret < 0)
>> + return ret;
>> + }
>> + av_packet_move_ref(pkt, bsfi->out_pkt);
>> +
>> + return 0;
>> }
>>
>> int ff_bsf_get_packet(AVBSFContext *ctx, AVPacket **pkt)
>> @@ -227,12 +253,9 @@ int ff_bsf_get_packet(AVBSFContext *ctx, AVPacket
>> **pkt)
>> AVBSFInternal *bsfi = ctx->internal;
>> AVPacket *tmp_pkt;
>>
>> - if (bsfi->eof)
>> - return AVERROR_EOF;
>> -
>> if (!bsfi->buffer_pkt->data &&
>> !bsfi->buffer_pkt->side_data_elems)
>> - return AVERROR(EAGAIN);
>> + return bsfi->eof ? AVERROR_EOF : AVERROR(EAGAIN);
>>
>> tmp_pkt = av_packet_alloc();
>> if (!tmp_pkt)
>> @@ -248,12 +271,9 @@ int ff_bsf_get_packet_ref(AVBSFContext *ctx,
>> AVPacket *pkt)
>> {
>> AVBSFInternal *bsfi = ctx->internal;
>>
>> - if (bsfi->eof)
>> - return AVERROR_EOF;
>> -
>> if (!bsfi->buffer_pkt->data &&
>> !bsfi->buffer_pkt->side_data_elems)
>> - return AVERROR(EAGAIN);
>> + return bsfi->eof ? AVERROR_EOF : AVERROR(EAGAIN);
>>
>> av_packet_move_ref(pkt, bsfi->buffer_pkt);
>>
>> --
>> 2.26.0
>>
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